You'll need 67 votes in the Senate and 290 votes in the House to repeal it while Obama is in the White House. Winning 26 new GOP members of the Senate and 110 plus new GOP members of the House while holding all of the current GOP seats in Congress would be quite a feat.
I'll be happy if we have majorities in each house of Congress and defund the worst provisions of Obamacare for now. Getting veto-proof majorities is no easy trick, although the Senate might be possible by 2014. A GOP controlled, filibuster-proof Senate, seems very possible by 2014.
I don’t think it would actually take 290 seats in the house and 67 in the senate to override an Obama veto. If we got within 15 or so of 290 in the house and even as far as 55-56 seats in the senate, dems up 2012 (all the house, 1/3 of the senate) would crap their pants and abandon Obama and Obamacare like rats from a sinking ship.
Very tall order, of course.