My guess: Sometime in January or February, the Mac Mini and iMac will be quietly updated to use the same new NVIDIA chipset that the new laptops all use. They will replace their DVI ports with HDCP-compliant mini-DisplayPorts. There won’t be any other major changes or redesigns in this update.
Then, as soon as Intel can deliver them in quantity, the Mac Pro will be updated to the “Gainestown” (Nehalem-core) Xeons. The new models will come in 2.93 and 3.2 GHz configurations, both using two quad-core CPUs. The video cards will be updated to new HDCP mini-DisplayPort models as well. The price points won’t change. This will probably be around February-March and will be separate from the Mac Mini/iMac updates.