With the new Xserves standardizing on 2.26, 2.66, and 2.93 and not including the 2.8 and 3.2 Nehalems, I think we can safely assume no silent speed bump will occur in 2009 for the Mac Pro line...
You're probably right about the lack of speed bump but I'm not surprised that Apple didn't put a 3.2 in the Xserve - Intel advertise it in their product literature as being specifically for work stations - it is probably a bit too hot-running to fit well in a server.