With Windows 7 and Windows Server R2 release Client and Server are in sync again, this was the case back in NT 3.1 in 1994, NT 3.51 in 1995, NT4 in 1996 and Windows 2000 in 2000. With Codename Whistler Windows XP (NT5.1) and .NET server (later named 2003, NT5.2) release went out of sync. Windows Vista (NT6.0) and Windows Server 2008 (NT6.0) the kernel got back in sync (not the release).
Windows 7 which is actually NT 6.1, so codename Windows 8 is NT 7 :-).
If the next release goes according to plan we will have a new release of Windows client and server somewhere in 2012 codename “Windows 8”. Job offers at Microsoft already start mentioning Windows 8. So according to the Server Release Cadence Windows 9 in 2015 Windows 10 in 2018 🙂 Well it is still a long time, let’s enjoy Windows 7 and 2008 R2 for a while!