Visual Studio 2010 will ship with a 32bit version, and no 64bit version. My team built a very smart layer into Visual Studio 2010 to enable designers and debuggers that work with 64bit Office 2010 and 64bit SharePoint Server 2010.
For a good explanation of why the Visual Studio team chose to only build a 32bit version for the next release, you can find a blog post by Rico Mariani titled “Visual Studio: Why is there no 64 bit version? (yet)”
SharePoint Server 2010 will be 64-bit only. You can learn more about the requirements of Microsoft SharePoint Server 2010 on the SharePoint Team Blog entry “Announcing SharePoint Server 2010 Preliminary System Requirements” If you plan to build solutions for the next generation of SharePoint Server, then I recommend budgeting to purchase 64bit hardware.
-Christin Boyd, Program Manager, Visual Studio