I wrote over at PostPartisan this morning about the question of whether Republicans would, if they get unified government in 2013, get rid of the filibuster. I don't think they would, but I do think they'd tinker around the edges quite a bit.
To add to that...you know what would probably make it less likely for Republicans to move against the filibuster? If Democrats, starting with the president, made filibuster reform a major issue this year. The truth is, three years in, Republican Senators have been forced to make shockingly few defenses of the filibuster and their use of it. They've for the most part treated the 60 vote Senate as something more or less as old as the republic, rather than something built in recent decades, with the big steps coming in January 1993 and January 2009.
Now, I do expect majority parties to move over time to an anti-filibuster position (and vice versa). But I also think that politicians tend to feel constrained by their promises, and the most specific and high-profile those promises are, the more politicians are constrained. So given that a Democratic push for filibuster reform this year would almost certainly spark a strong Republican reaction, it would at the same time slow the odds of rapid reform in 2013 if Republicans win big in November.
The flip side argument is that Republicans would, after opposing reform this year, use Democratic rhetoric as an excuse for action after the election. That doesn't sound right to me...if Republicans are ruthless enough to immediately flip as soon as the election is over, I doubt they would care much about the justification.
Of course, this puts aside the possibility that one side might decide they want a more majoritarian Senate, and would be willing to give the other side the first chance at it in order to get that procedural change enacted. Mainly because I think that's unlikely to ever really happen.