Intel should soon be releasing a minor revision of Xeon CPUs suitable for the Mac Pro. The new CPUs will allow marginally faster memory and slightly higher clock speeds for some parts, as well as up to 18 CPU cores on one chip.
In terms of performance vs current offerings, the new CPUs are of marginal interest. That is, unless Apple chooses to offer up to the 18 core option, which could be attractive for those looking for maximum grunt for things like video processing. But an 18-core CPU is ~$4700 for the CPU alone (Apple would get it in quantity for less, but it would surely not be sold for less than that in the Mac Pro). Of course, a “pro” Mac Pro would allow dual 18-core CPUs for 36 real cores, along with memory slots for up to the 768GB of memory the CPU is capable of addressing.
There is an outside chance that Apple will do something “interesting” in a revised Mac Pro (non CPU stuff). Possibilities could include higher capacity SSD options, revised GPUs, early support for emerging video standards (e.g. 5K), or a larger trash can supporting dual CPUs and more memory (highly unlikely in the current consumer driven approach).