Forget 64-bit, Microsoft has already been exploring 128-bit support scenarios for future releases of Windows. Of course, with Windows 7 and Windows Server 2008 R2 wrapped up since July 22nd, 2009, the official release to manufacturing date, the 128-bit wave will not affect the successors of Windows Vista and Windows Server 2008. Fact is that, with the mulling of 128-bit support for Windows, Microsoft is already looking as far ahead as Windows 8, the successor of Windows 7, and even Windows 9, which means that the Redmond company has put together at least general development directions for the next generation of Windows platforms well into the next decade.
This because Windows 8 is not expected ahead of 2011, with Windows 9 following it in 2014, in the most optimistic scenario possible.