If you have been reading the many posts about this week's TechED that is going on in Orlando, you may have noticed the references to Visual Studio 2008 (a.k.a.) and SQL Server 2008 (a.k.a. Katmai). I'm not sure if I've been been paying attention or not, but I don't remember any formal announcement on this name-change. In fact, the April CTP still mentioned Visual Studio 2007 in its setup. Nonetheless, it does fit nicely in the pattern that has been used for all editions of Visual Studio.
June 6 Update: It is now official...see here.
June 7 Update: There is FAQ explaining how Visual Studio 2005 and 2008 co-exist with eachother.