"For larger teams and those who require integrated work item tracking and other software configuration management features, we've got a shiny, new Team Foundation server that we think you (AND the Microsoft Windows development team) will be using for many years to come." -- Korby Parnell.
Actually, the post was mainly about Visual SourceSafe, a product I cannot in conscience recommend to anyone. Any tool whose Best Practice guide recommends that you run a scheduled repair utility, so that the database corruption doesn't grow excessive, is just poor - particularly one you're relying on for your core business assets. Now, in fairness, a lot of the corruption experienced by many people is down to the usual culprits: flaky hardware, bad implementations of network file sharing in Windows 9x. Fundamentally, though, you have multiple remote clients modifying the same files - which has traditionally also caused problems for Microsoft Access - with no decent blocking lock support.
We know that Microsoft were using an internal system before Windows 2000 that basically forced a serialised development style; when it went into the final stabilisation stage, and the team were beginning to look towards Whistler (eventually Windows XP/Server 2003), they started to use a new internal system called SourceDepot (Source: Mark Lucovsky's USENIX presentation "Windows: A Software Engineering Odyssey" [PPT, HTML version]). Rumour has it (never officially confirmed) that SourceDepot is derived from a Perforce source-code license. It's a pretty good bet that Microsoft aren't allowed to sub-license their mods to anyone else.
VS Team System's version control component (code-name Hatteras) looks surprisingly (but no doubt superficially) like SourceGear Vault, from a descriptive point-of-view. Eric Sink (CEO of SourceGear) indicates the impact he thinks this will have on Vault (basically, innocent bystander caught in the cross-fire between IBM's ClearCase and Microsoft). So MS may be continuing in their long-standing tradition of dog-fooding - or Windows may have again grown out of its source control solution.
However, the future looks decidedly dim for SourceGear's SourceOffSite - similar features appear to be destined to appear in VSS 2005.