I think Stevens is going to retire. If Ginsberg's cancer is flaring up again that could well be two seats. Ginsberg may happen before the elections.
The 4 (hopefully) conservatives judges do have a 15-year youth advantage over the 4 liberal justices. As long as we can keep the white house, it is only a matter of time. I really don't think any of them will retire. If one did, that would send shockwaves to the liberals. They would be in panic mode like we have never witnessed before in history.
There is no way either of these two will voluntarily retire and let Bush name their replacement. They know the balance of the court as well as anyone.
It's really not fair to get a guy's hopes up like that. :-)
Heck... if Bush replaces Ginsburg with a Janice Rogers Brown (or similar)... I won't even complain if he wants to put Gonzales on the court for Stevens (still a massive move to the right of course).
The really sad part is by the time we get to those appointments, the press, the liberals, our own GOP people, and some Freepers might have weakened Bush so much he may not get who he wants.