It seems like most Microsoft products have gone from version 3 to version 11 in the same timeframe as VSS has stumbled from 6.0a to 6.0f...
So it's no surprise that there has been a lot of excitement about the news of a NEW version of VSS; and also of some cool 'Team' features in VS.NET2005... Imagine the confusion, then, as it becomes clear these are not the same product!
Visual Studio Team System is a good place to start reading about VSTS -- but not necessarily VSS. The MSDN Team System page has a good overview.
I like this quote "So VSS is to Hatteras[Team System] as Access is to SQL Server" (from somewhere here I think) except VSS doesn't have a cut-down, database driven back-end that easily migrates/scales to VSTS, like Access → SQL (??).
The Microsoft Visual SourceSafe Roadmap explains a bit more about SourceSafe 2005 -- basically sounds like the version upgrade we wished for around 2000... hard to see it lasting to the post-Whidbey VisualStudio release (i.e. beyond 2006).