As soon as the Republicans take the Senate back, they'll abolish the filibuster on day 1. That should be obvious
I don't think they'll abolish the filibuster. If they gain the majority in 2012, there's a good chance the Democrats take it back in 2014, because the GOP's majority would be of about one seat or so, and the fear that Hillary Clitnon would defeat Romney in 2016.
I hope they do abolish the filibuster -- or at least reform it to end the
de facto rule that 60 Senators are needed to pass most legislation. It will be a popular reform (or abolition) across the political spectrum. We are left to wonder why the Democrats didn't abolish or reform it when they had the power in 2009-10.
I doubt the Dems can retake the Senate in 2014, though I agree with you that "the GOP's majority would be of about one seat or so". From what I can tell, in 2014 the Dems have to defend 20 seats -- including five in the South and two in solidly red states (MT and SD) -- and the Republicans only 13.