Yes, you can time your purchase if you're building it yourself. I'm not talking about that. I'm talking about trying to time your purchase of CPU's to fit Apple's roadmap. As I said earlier and as you also mentioned it's probably best to wait till the next MacPro release and stay away from the first one. Although are you sure Apple doesn't have the latest Motherboard revisions already? I'll wait to see what happens with this first release and when all the facts are in then i'll decide which way to go.
Oh for sure but I run OS X on my desktop as a Hackintosh. Apple has a nice build quality advantage on the laptops (Touchpad is nicer, case is nicer, thinner and lighter than competition, great battery life etc) but on the Desktop it doesn't matter what the system looks like.
So for me building a hackintosh was better. I dual boot Windows 8.1 and Mavericks on it with everything working perfectly.
I think a few other people have gone this route waiting for Apple to update the Mac Pro.