You should be asking Intel where the suitable Xeon Sandy Bridge processors are. You're waiting on Intel right now. The estimated release date for those CPU's is Q4 2011 so they should be here relatively soon.
I forgot that the Mac Pros have dropped behind in the processor. Finally Sandy Bridge when the rest of the Mac lineup is going to Ivy Bridge. I guess that I have over a year wait yet for an Ivy Bridge Mac Pro. I'll have to keep my 1st Gen Mac Pro until it is 6 1/2 to 7 years old. I will probably add an ivy bridge 17" if Apple doesn't screw it up by making it thinner & making it less powerful. I use the optical drive a lot, but my main reason for wanting it kept is so that I can take it ot & adding a second hard drive. It's actually the space inside the MacBook Pro I do not want to lose. I used to carry a setup that weighed in at about 50+ pounds. So a little over 6 pounds for a 17" MacBook Pro is light enough for me.