Gerrymandered district lines will be their most effective in 2012, and slowly start to lose efficacy as more elections roll around (and, more specifically, demographic shifts happen). With the right candidates (and wrong Republicans), Democrats could break through in 2016. And, if an unpopular Republican wins the 2016 race, then the Dems will have a terrific shot at the House in 2018.
But the thing is, the Democratic coalition is shifting toward being more, not less packed. The Obama 2008-Romney 2012 areas are all outer suburbs and rural areas. A lot of the urban areas went from 75% to 80%. The only really promising areas for additional house gains are Florida, the rural West and some suburban VA districts that probably weren't gerrymandered enough.
The suburban PA districts would be ripe for Dem pickups, as well as a few in New York and a couple in Michigan.
Suburban PA, though leaning Democratic at a federal level, is still mostly Republican in local races (affluent, socially moderate whites). They go gaga for Christie types.
