If this actually happens, I'm not sure that enough Democrats will vote to override the expected Presidential veto. However, they can try and if it fails, then they can go in and start repealing specific parts of the ACA, such as the medical device taxes and others.
Dems are running from Obamacare. All the GOP needs to do is pick a few in purple states up for re-election in 2016. The GOP is looking like it will have 54 seats by the time the LA run off is done. If they get two independents to side with them, they will need 4 Dems wanting to keep their seats to over ride a veto.