Obama's victory likely drove the last nail into the coffin of anti-Obamacareism.
By then, most of the bill will have kicked in and people will be enjoying its benefits. Certainly some will resent it, but probably not the constituency which drove Obama back into office.
Is it safe?
A perspective from the UK, where we've had the NHS for over sixty years. It's far from perfect - bureaucratic, clunky, with examples of incompetence and waste - but it's highly valued and no politician dares to suggest we should do without it. In fact, the Conservative Party kept plans for a reorganisation top secret through the last election campaign as they knew it would be a big vote loser (could still cane them in the next election if people start to see a decline in its standards).
My guess is that the more Americans get used to Obamacare the more they will turn on anyone threatening to take it away.
I was surprised at how little Obama and the Democrats explained it or defended it.
I'm also shocked at how easily those with health care live with the idea that so many people have inadequate health care (or none) as long as it keeps their own premiums and/or taxes lower.
A funny tidbit of history is that the Beveridge report was translated to German and dropped over Nazi Germany during WW2 as propaganda, and I believe it was von Papen which brought it to Hitler and said "This plan is superior to ours in all ways."
Obamacare is safe as a starting point to an extension of the public healthcare system, it's always easier to get policy introduced than retracted.