Depend on what you do. 5DII is probably good for many many years.
Also, B&H photo have a $500 rebate on 5DII if you buy a high end printer at the same time. Sell the printer, and you have a brand new 5DII for around $2000.
From the net, people are saying that the proposed 5D MKIII will be like a heavy armed "full frame" 7D + stronger sensor and it will be released as early as next February.