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?
I only listed the conservative Senators because polls suggest that they are in trouble. Chafee will likely have a much easier going in the general election than the primary, so losing him probably isn't in the cards.
If we had to lose someone, and if it were up to me, then yes, I'd pick Chafee.
But anyway, as to the Court, we've already lost McCain and Chafee with regards to the nuclear/constitutional option, and its hard to imagine either changing their position. Well, I guess I could see McCain doing so if his vote were the deciding one, as it would ingratiate him with the social conservative base like nothing else could. But looking at Republican members of the Gang of 14, Graham has promised to vote for the 'nuclear' option should the Dem gang members join a filibuster on ideological grounds. DeWine and Warner have hinted at the same, so even accounting for non-gang member Specter, we could conceivably still pull the constitutional trigger should it be necessary.
However, if we lost Santorum, Burns, and Talent, and all else was equal, then we'd have 52 senators, and the Northeastern trifecta of Chafee, Collins, and Snowe alone could make impossible the nuclear option.