Situation 1) Apple doesn't care about mac pros anymore and won't update them even though all the parts are available until they feel like it
Situation 2) Apple is getting early access to light peak and the reason they are delaying new mac pros is that they are working with intel trying to build light peak into them.
I hope for door number 2, as I will be in the market for a Mac Pro around year's end, when I would think that this tech would start coming out (or at least get announced).