The commercial real estate market has been buzzing for months with rumors that Amazon.com would lease office space in three downtown Seattle buildings. Now city permitting records indicate those rumors are true. If they are, Amazon will be taking down around an additional 515,000 square feet of space. This would boost the company's footprint to around 8 million square feet of space in Seattle when counting what the company owns and leases, what Vulcan Inc. has under construction for Amazon…