Hot off the presses at the MS SharePoint Team Blog is the preliminary requirements for SharePoint 2010. As most of you probably have known, MS has been saying for a while that, going forward, 64-bit is the path and 32-bit is going the way of the dodo. On top of that, you will also need to either be running 64-bit SQL Server 2005 or 2008.
More and more tidbits of information are coming to light...stay tuned...
-M