No, the retail version of Tiger is PPC only, so you won't be able to install it on a mac pro. Also, all models that are updated after a new OS release are incapable of running previous versions of the OS(which causes endless consternation for corporate users, but....) so if you wait till the model refresh, you won't be able to install Tiger on that machine officially.
Theoretically there could be some hacks to do so, but they would be unsupported, lacking drivers for whatever new hardware is in there, and probably not worth while.
This is slightly worrying news to me: I want to buy an 8-core Mac Pro, but like practically everybody else here, i'd rather wait until the upgrade that MIGHT appear in January before I buy. However, it's vital for my work that all my apps continue to function as normal, and the transition from my old G4 to my new Mac Pro is as smooth and trouble-free as possible. For this reason, I'd prefer to wait for Leopard to be more stable before I install it.
But, if I wait for the MP upgrade, it will most likely have Leopard pre-installed, which might cause me problems. What would be you folks' advice? Buy a current 8-core now (at a bargain price) because it comes with Tiger? Or still wait for the upgrade (that might have more bang for my buck, but could end up being a waste if some apps don't work properly in Leopard)?
Apps vital to my work are Photoshop, InDesign, Illustrator, QuarkXpress, Poser, Bryce, Painter, Acrobat, DreamWeaver, DataRescue, Word for Mac, and Toast.