I believe AMD is going to be releasing the new CPU's before Q2 of this year, so honestly, unless your insanely loaded with cash, I'd wait. I'm not sure if they will be using the new socket, so if they are be prepared to dish out the additional ~$150 for a new motherboard.
I'd definately be waiting at this point. If you have money saved up, keep trickling the money into a pool to see what the M2 socket has to offer. It might rock. Or, it might wither and die almost instantly. Who knows. It won't hurt to wait till we get closer to the debut date.
If it would be a good 10-12 months away then I'd just stop buying so much soda at work and save that money up. I could probably have an FX57 San Diego by May if I did that... geez.
I'd probably go ahead and get the 2x4200, but that's just me. I mean, if the M2 gets launched and dominates, it still doesn't make your processor obsolete... It'll still be just as fast as it always was (which is probably more than anybody needs anyway. It's merely a "keeping up with the jones' " thing at that point.