I did a similar thread not so long ago, so here's my 2 cents based on MY decision.
If you're unsure what to do then you should probably wait, here's why.
1. The 5D Mark III should be announced sooner than later.
-The Mark II was released 2008, it obvious that a new one is on it's way and lading sooner rather than later (2011). I know the Mark II is selling well and that the Japan tragedy affected a lot of stuff but time goes fast and you should see a new one in the near future.
2. This should be a worthy upgrade
- We're not talking about a new side camera like the 60D, 600D or T3i, all those are based on existing technology. New Canon cameras should arrive with their new Digic V processor along with many cutting edge features and fixes. The Digic IV was releases in 08' and technology improves very fast, I don't think you want to be stucked with that when you could wait a bit longer.
3. If you're having this thoughts right now...
- When the Mark III gets announced you'll probably regret spending 2,000+ dollars on the 5DMKII.
That's just my opinion, I'm personally waiting for the 5D Mark III. I really want a camera right now but I'm short on money and don't want to regret buying an old camera just because I couldn't wait. If you really, really, REALLY need the camera right now..then go for it.