Despite what Bill Gates said in Miami, Windows 7 is timed to come out by the end of January 2010, not "in the next year or so." Here's what Sinofsky, Windows engineering head, had to say on the matter.
Windows 7 is an evolutionary improvement to the kernel in Windows Vista and Windows Server 2008, not a wholly new MinWin kernel that has been under development.
Windows 7 will be available in 32-bit and 64-bit flavors. Sinofsky did suggest that Windows 7 will build on the architectural changes in Vista, suggesting that many of the changes may be the kind of features that are available out of the box, as opposed the kind that take years as developers build them into their products.