If it goes down, no Congress will ever take it up again. It will become the third rail of politics. Obama spent all of his first term political capital on this and his second term will not be with a Congress nearly as inclined to lift a finger. Democrats saw that it cost them the Speakership in 2010, they are not going to let this issue burn them again. Republicans will not do a thing about health care, mostly because they honestly don’t give two shits about it.
As far as 2012 goes, it deflates the fixation on killing Obamacare. It also erases the base Republican knuckle-draggers’ biggest concern about Romney. So it’s a wash. Republicans were due to give the House back anyway, this will make it harder to hang on. It also makes it harder for the Democrats to lose the Senate, however hard they try.