The SharePoint Team has just released the preliminary requirements for SharePoint 2010. And yes it will be 64 bit only as you probably have heard before. However, there are other requirements as well now. Most prominently is that it will require:
- Windows 2008 or Windows 2008 R2 x64
- SQL Server 2008 or SQL Server 2005 x64
- Require Internet Explorer 7 and above for content authoring
So if you are planning to deploy a new SharePoint environment now, you should plan for these requirements now for future upgrades to the next version and it will definitely reduce future upgrade acitivites. More details on the preliminary requirements could be found at the SharePoint Team Blog :
http://blogs.msdn.com/sharepoint/archive/2009/05/07/announcing-sharepoint-server-2010-preliminary-system-requirements.aspx