With the recent rumors regarding a Mac Pro refresh coming shortly, and the fact that there are no Sandy Bridge Xeons out yet, I'm guessing that it is quite possible that Apple could release a cheaper (and maybe smaller) single CPU Mac Pro using i7 Sandy Bridge CPUs.
But maybe I'm just dreaming. To me, it would make total sense for Apple's product line to include a "display-less iMac", where you could add a couple of HDs and and PCIe cards and switch out the GPU. In other words, a standard PC as we've always known them!