I've been lurking the forums for a while, but this is my first actual post here.
Anyway, I am definitely going to wait for the revision for the Mac Pro before I make my purchase. Although a new version will always eventually come out and outdate your purchase, I'd rather buy when the revision first comes out, rather than buying right before the next revision. This especially holds true for me, since I plan to dump over 3k on the computer alone (and that's including an education discount and no display), and I want my money's worth.
What I think will probably happen is that the dual 2.0 GHz dual-core Xeon setup will be ditched, with the dual 2.66 GHz dual-core Xeon setup being the lower end, the dual 3.0 GHz dual-core Xeon being the midrange, and something like a dual 2.66 GHz quad-core Xeon setup filling the high-end. Depending on the price, I might get the dual quad-core setup, but if my predictions are correct, and the octo-core setup is much more expensive than the other options, I'll probably end up getting the dual 3.0 GHz dual-core setup.
What I'm mainly hoping for are other upgrades along with the processors. Sure, dual quad-cores are nice, but how about a refresh on the video card selection and dare I say it, the possible availability of a sound card option? Since the Mac Pro is used by many people for content creation with programs such as Final Cut, Logic, etc., it's beyond me how a workstation of this caliber doesn't offer the option of an internal sound card, as onboard sound from the motherboard is rather pathetic in comparison.
Also, better pricing on the RAM on the next revision would be nice too, as I can't seem to justify getting anything more than the 2 GB option from the Apple website without sourcing the RAM and heatsinks myself. A display update would be awesome too, hopefully lowering the prices and maying refreshing the lineup. The number of days since the Mac Pro refresh and display refresh are equal, so hopefully they will get updated at the same time. I know for a fact that if the displays aren't updated, I'll buy my own off of NewEgg or something, as I can easily find something better for less than half the price with Apple's current display lineup (14 ms response time? come on, Apple, get with it).
Basically, I'm just mainly waiting so my money will buy more for the same price or maybe even less. The Mac Pro revision better come by NAB at the very latest, or I'm going to be extremely disappointed, and I'm sure most of you would be as well.
As far as the possibility of Leopard coming with the Mac Pro revision, it would be cool, but doesn't matter to me a whole lot. My parents have 4 Apples at their house, and I can just persuade them to get the family pack for their Apples with Tiger and then I can use the 5th installation. I do, however, think that it would be best if Leopard comes on the new Mac Pros, because that would be less of a hassle for people.