Always wait until after a big show. Macworld San Fran is Jan. 15, so a month and a half won't kill you. But you will kill yourself if you buy now and they announce bigger/better/faster machines for the same price within weeks of your purchase. Happened to me years ago, and I still have scars...
B)
Why? Why have such an overreaction? There'll always be a better/bigger/faster machine out there 99% of the time, so why beat yourself up over it? Is it really that important to you to have the absolute best machine on the planet? Surely what's important is to have the best machine you can afford that will do what you want it to do at the time you want it, no more no less?
I'm getting an 8 core Mac Pro before the end of the year, no matter what; if a new machine comes out a couple of weeks later, what's the big deal? All I want is a good machine that will do what I want and have a working life of, say, 5 years. When it's near death, I'll buy another.
After all, why worry about resale value? By the time I'm ready for a new machine, it won't be worth much anyway, just like my G4, even with its dual processor and souped up graphics card. Who'll buy a G4 now? It isn't about "value for money", the Mac Pro will be brand new whether I buy it tomorrow or in a month/2 months/3 months. Sure, if there was a definite date for an upgrade, of up to a month away, then maybe I'd wait, just to see what was on offer. But the current 8 core will do me just fine, and it might even come down in price when there's an upgrade. It's not vitally important for me that I have the latest/best machine out there, and I suspect that's true of most people.