Paul Thurrott has an interesting article from outlining his thoughts on Windows 7, specifically with regard to Windows Home Server.
Here’s what we do know. Windows 7 can and should be considered Vista Release 2 (R2). In fact, I think Microsoft should market the business versions of the OS under that very name. Beginning with the release of Vista SP1 and Windows Server 2008, Microsoft no longer forks its Windows code tree for new releases. So the next versions of Windows client (7), Windows Server (2008 R2), and Windows Home Server (WHS) will all be based from exactly the same code. Microsoft will simply combine the right components to create the Windows version it wants and ship it. It’s a much simpler system than before.
If you follow Paul’s thinking, we may never see a version of Windows Home Server based on Windows Server 2008, and instead, “Vail” (the codename for the next version of Windows Home Server) will leap over that release and synchronise with Windows 7 and Windows 7 Server (or whatever it will be called).