It is far too early to be predicting 2012 or anything. However, the fact that the Dems have 23 seats up and the GOP only 10 is going to make keeping things even kinda difficult.
I think that is the key. Even if Obama would win in a Democratic landslide in 2012, it would be likely that at least some of those will flip.
2014 is almost as bad, with 20 Dem seats up. That leads to an interesting situation. Obama is re-elected in 2012. There is a bloodbath in 2014, in all probability.
Obama loses in 2012 and there is a bloodbath in the Senate in 2012. 2014, there may not be a total disaster in the Dems in the Senate, but there is still a likely loss.
It might be probable to say that there will be three Senate Elections with GOP gains.
And yes, that is one of the signs of a realignment. 3 years of gains in at least one House, with a switch of control.