1. The Presidents' party have won House seats in only three mid-term elections since 1818. While it seems unlikely those conditions can be replicated, let's assume that the President's approval rating jumps up in the 60%+ range. The President's party won 8, 4, and 9 seats in those elections. The edge, when it did exist, was small, not big enough to flip the 17 seats they'll need in 2014. People are unhappy with the President in mid-terms.
2. Republicans have a more pronounced advantage in the mid-term electorate than they have in the past. That structural shift may be part of the reason Republicans gained House seats in 2002.
3. We've never had congressional district maps that favor the Republicans like we do now.
So, if any party was going to defy point one, it'd be the GOP, per points two and three. It won't happen with a Democratic President.