Palin/Gingrich 2012! The biggest landslide in US history. For the democrats.

Other than that, while I agree with your central premise about the economy being at the root of the matter, degsme, I would expect the GOP to pick up a few seats if the economy is doing well and to pick up more if not.

Its usual for the opposition party to pick up seats in an off year election, the demographics of people who are more likely to vote in such an election favors the GOP, and due to the strong democratic showing in the past few elections more battleground seats are currently in the hands of democrats than republicans.