At least now, with the current Senate, we know we can force a vote on a Sup Court justice the caliber of Alito (though as I say this, I wonder if such a nominee would get as many votes for cloture if he were the potential fifth conservative on the Imperial Court, instead of the fourth like Alito was).
If the GOP loses 2-3 seats, and keeps a Chafee-proof majority, it would still likely be disastrous towards the cause of righting the Court, because those loses would likely be reliably conservative votes like Santorum, Burns, and Talent -- in that order of likelihood.
The attainment of a conservative Sup Court, loyal to the Constitution, would be a historic achievement. We lost that opportunity with the terrible record of Reagan and Bush the Elder -- just 2/5 good picks -- but now we may have a second chance, and we stand on the verge of it. We just need one more (non-Scalia or Thomas) retirement, and then it will all depend on Bush and the Senate.
...assuming of course that Roberts and Alito turn out as we hope, and as promised.
I'm not suggesting that the loss of conservative Republicans would be a good thing--it clearly wouldn't. But would the loss of Chafee and McCain be a disaster?