I have a test machine with Windows Server 2008 r2, can I upgrade it to Windows Server 2012 (AKA Windows Server 8).
With all previous release of Windows, there is a clear pattern that you can upgrade one Windows version to the next immediate version directly. E.g. XP--> Vista. Vista--> Win7. Server 2003-->2008. So I believe it is safe to say that you can upgrade server 2008R2 to Windows Server 8 directly.