The Democrats probably narrowly retake the House in 2014. Romney, barring any primary challenge or serious right wing third party run, gets re elected in 2016 against Hillary Clinton. 2018 and 2020 are bloodbaths for the GOP though.
I think in 2020, Mary Landrieu, Deval Patrick, Ron Wyden, or maybe Cheri Bustos beats Paul Ryan handily.
Sherrod Brown is more likely to hold on in 2018 TTL as well (so long as he holds on in 2012), so he's a possibility and so are other Democrats who'd be elected or re elected in 2014 with a Republican in the White House.