We got to know about the new LEGO Technic set names for the 2H 2015 a couple of weeks ago. 
42040 - Fire Plane
42042 - Crawler Crane
42043 - Mercedes Benz Arocs 3245
Among my first impressions and my best guesses, I was convicted about a new version of 8288 Crawler Crane from 2006, eventually at a larger scale and some motorized function.
In what regards the MB Arocs was concerned and from the several possibilities we can see from the images available online, I thought about a dump truck. It could a nice fit with the last flagship 42030 Volvo L350F Wheel Loader. This would eventually boost sales for both sets, but however and due to the large scale of L350F among Wheel Loaders it would fit a lot better with some sort of mining truck or another larger MB heavy duty truck than with an Arocs truck. This would fit much better with some kind of smaller scale WheelLoader (like 8265 which unfortunately it is not selling for long. So all the possibilities were open again (Tow Truck, Crane with Tipper, Concrete Mixer, Dump Truck, etc...). Even we could get some version with 3 or 4 axles, although a 4 axle is more likely for a $200 flagship.
Only viable possibility for the wheel size to be the use of same tires and wheels as in 8258 Crane Truck and 42009 Mobile Crane Mk II.
Also it stood out that a simple dumper would turn a bit too short in terms of available functions for a Technic flagship...
As for the Fire Plane there is not much to expect. From the set number it should be the smallest in the season with not much functions. Some propellers, bottom doors for the water tank, eventually some working flaps, rudder or retractile landing gears. Most likely not motorized.
And finally as you may have already noticed in some forums, there are already a few images circulating in the sub-world of some die hard Technic fans... This has been more than expected as we approached the new year.
As you also know TLG is always much concerned about leaks, so we can't publish any watermarked images, but we can talk about them if we came to see some. At least this has been the agreement!
Please bear in mind that as usual by this time, images are quite small, very blurry hence with too few visible detail. Also these are clearly not the final box artworks, what means some information may be incomplete, not precise or subject to be changed in the final product. So please take all the info below as just a bit more than rumors.
And let's take into the details...
42043 - Mercedes Benz Arocs 3245
This is indeed the new Arocs truck with its typical front grille and MB logo. Likely a sticker on a round tile but I wish it would be printed as we also can't see many more stickers, apart the license plate.
It is a tipper truck with a crane behind the cabin, like 8258, although this did not include the tipper.
The truck is predominantly white with light or dark bluish gray elements. The crane has a claw and it is red.
In terms of Power Functions, the box shows one Battery Box and one L-Motor (remember some motors information have been wrong in some preliminary box artwork before).
And it also shows the are several pneumatic elements in this set (presumably 4 of them) which makes this mainly a pneumatics set! 
Now the best part (sit if you are not already sited)...
We can see three different cylinders size!
From the apparent proportions I'm assuming the one in the middle is the regular pneumatic cylinder (Design ID: 47224) and so the other two in the top should be a longer version of this.
Regular cylinder is 7 - 10,5L and from the proportions I guess the new one could be something like 9 - 14,5 (tbc).
We should have also one pump. A small one to build a motorized compressor. The last element doesn't seem to fit with the new small pump introduced with 8110 Mercedes-Benz Unimog U400 (Design ID: 99798). Rather it seems a bit shorter and thicker. Can it be a new short pump with 2L diameter!? I can't be sure but it would make some sense, as longer and several cylinders will require more air, and this is one way to produce it a reasonable pace.
So you see, some clues here but also significant doubts about what we will get...
The crane itself looks the have three sections with a clam-shell bucket in the tip. Only one pneumatic cylinder is clearly seen in the crane arm (parallel to the first section which folds/unfolds the second section), but I guess two/three additional ones are also possible - One in the column to fold/unfold the first section, one to extend the boom (second section) and one inside the clam-shell to open/close it.
This makes up to four cylinders and remember we can only see three (+ one pump) in the box. We could easily live with some crane arm geared functions to accommodate the difference, although the apparent amount of pneumatic houses around the crane arm sections really puzzles me...
Although not clearly visible, at least the cylinder to extend the third section seems to be present, due to the hoses around and the way the lay around the crane arm. It can be manually extendable though, with the hoses going to the clam-shell.
Them we remain with another doubt... What about the tipper? Does it tip or do not tip
There is no single evidence in the box that it does, but one should expect it does...
Them I'd also expect it to be driven by one or two pneumatic cylinders (like in real Arocs if we think about hydraulics as pneumatics...). But these are already too much for those shown in the box and for a single set, so if it really tips I guess it will use Linear Actuators.
Now let's see about the other functions...
We can see two wheel axles in the front (both steerable). There is also an extendable out-trigger behind the second axle, which makes me think about gear racks now in LBG color
It is not really possible to clearly see behind this, but I still guess there are another two axles not seen. It wouldn't make too much sense to have two axles in the front and just one in the rear...
The wheels/tires definitely look to be the same as in 8258.
There is a big distance from the mudguards to the tires which suggests the presence of some kind of suspension.... wondering, but we will see!
There is no evidence of the presence of any piston engine in this model, but it may be there... We will also see!
The cabin is 17 studs wide, like it was the 8258 too, which means both trucks are in similar scale.
The tipper looks to be at least 33 studs long.
So in terms of functions, let's list the possibilities:
4 rolling wheel axles
Two steering front axles (HoG)
Suspension - ? (likely)
Pneumatic motorized compressor (via switch box)
Extendable outriggers (via switch box) - motorized ? (likely)
Tipper tilt? (via switch box and LAs or pneumatics) - ?
Cabin tilt - ?
Cabin opening doors - ?
Fake engine under the cabin - ?
Tipper open door -?
Rotating crane arm - motorized (via switch box) ?
Crane arm first section folding pneumatic ?
Crane arm second section folding - pneumatic
Crane arm second section extension - pneumatic ?
Clam-shell opening - pneumatic ?
And this is it! If we consider we should get 2 or 4 motorized functions selectable via switch box, we need to prioritize which ones they should be in case they're just two instead of four.
42042 - Crawler Crane
This is a crawler crane with lattice boom like 8288, but at a bigger scale, although without the second mast (hence smaller boom) which otherwise would mean an enormous set.
It is predominately blue with some white appointments like the cabin.
We can see a lot of blue Technic beams (inclusive in the lattice boom) and some blue panels too, like the newer version of the 11x3 curved panel (none of these 11x3 curved panels were released in blue before).
Due to the larger scale, tracks use the large links (Design ID: 57518), which seem to be used here in DBG color.
The is a Power Functions set of the shelf and the box indicates the presence of a Battery Box and also one L-motor as it seems to be.
The set includes a rock grapple made with the grabber claws (Design ID: 11953) used in 42006 Excavator.
I'm sure the the new clam-shell elements introduced with the Mercedes-Benz Arocs would fit also perfectly here, but makes sense to use some diversity in the sets that are in the shelves, so the designers decided to have both in different sets.
I'm sure this is something you're going to try! :D
The grapple opens via a manual knob/gear seen at his top. It wouldn't be possible to make this motorized anyway once it is suspended in the load lane.
Additionally we can also see in the box, grabbed in the claws, a latticed blue section which I guess it can be used to extend the crane boom, making it even longer.
Given this details and with one single motor, the functions we can expect to see motorized are the boom elevation and cable drum to raise/lower the rock grapple or whatever you install in its place.
Thus overall function candidates for this set are:
Manual tracks push pull
Manual superstructure rotation
Manually extendable boom, by attaching modular sections
Manual rock grapple opening
Motorized boom elevation
Motorized cable drum (lower/raises rock grapple)
No details about the B-models so far!
And looking forward to get additional details on these sets as well as the Fire Plane still unseen. Likely when the Toy Fairs will start again all over the world.