I have a feeling that half of those who upgrade will keep the 5DM2 as a backup camera. If you are professional, you will always always want a back up...if you are semi pro you may or may not dump it as soon as you upgrade.
My family photographer (no, wife doesn't trust my skill set yet) still uses 5Dc along with his higher end 1 series bodies. I pick his brain from time to time, and he has no plan to let go his 5Dc. His reason? He can make more money with his 5Dc than what he can get if he sells it. That's how he sees it.
When 7D replacement comes out (possibly fall of 2012, big if), I see 7D taking a big hit more than the 5DM2, which it already took a small hit. Yes, 5DM2 could still go down in price, but not that much.
If you are looking for 7D, might want to wait until replacement comes out.
But, while you are waiting, how many photographic opportunity are you going to miss? Are those photo ops worth $100-$200? If so, wait...if not, get the body and be trigger happy.