Intel brought out some Sandy Bridge Xeons already but they are too expensive:http://ark.intel.com/MySearch.aspx?s...graphy=32%20nm
Apple use the $294 W3530 (45nm) in the quad (8 thread) and $387 E5620 (32nm) in the 8-core (16-thread). There are no faster chips at the same price yet.
There are Xeons planned for the end of 2011 but that's quite far away and it makes sense for Apple to get Thunderbolt available to Mac Pro users, although they can possibly get a PCI card upgrade for now. There were faster chips tested out by Intel:http://www.brightsideofnews.com/news...s-a-catch.aspx
but I don't think that has any relevance to Apple's products. Same with the 10-core chip coming:http://www.pcworld.com/article/21999...irst_half.html
Whatever they do, it's likely they'll leave the entry-level the same for a while. I guess there's a chance they can get something in 22nm from Intel early like they did Thunderbolt but it's wishful thinking.
The best thing they could do is redesign it, keep the same CPUs, add Thunderbolt and lower the price.
For buying now, I'd check the benchmarks for the various Mac Pro models vs refurb. I'd go for the most modern CPU though. 32GB RAM seems like overkill but it depends on how much you use. I'd get faster RAM and higher density RAM has better resale and allows better upgrades but tbh, 4 x 4GB 1333 would likely do just fine.
The next updates should be the iMac and Mini in April. If an FCS update comes and Lion, it makes sense to have an updated Mac Pro but I wouldn't expect major performance jumps unless they are hiding something.