As Chait notes, the GOP has been wildly overselling the catastrophe of the approaching full implementation of Obamacare. For 26 year old single men (you, know, assholes), Obamacare will probably prove onerous (unless they get sick). For most people, they won't see a lick of difference in their health care. For those who were without... BONUS! Most importantly, we should continue to see an overall decline in the national cost of health care, which is the most important fiscal issue the country faces.
The problem for the GOP is that in a few years, Obamacare will be the status quo, and few people will want to mess with it. As Chait notes, the most successful GOP attack on ACA was that it would cut Medicare and result in "death panels". That these attacks were brazen lies did not diminish their effectiveness. But they were making a temperamentally conservative case against change, rather than an ideological conservative case against government involvement in health insurance.
In a perfect world, Obama spends his second term setting up the provisions in ACA and Hillary gets elected with enough coattails to bring in a Democratic House and we finally get a public option. Ultimately, in 20 years or so, I expect the US will have a single payer system. Ultimately, that was the point of the entire exercise in 2009-10. You can't get from Point A to Point C without going through Point ACA.
And this is why the GOP is so scared (and right to be scared). This is indeed a slippery slope, just as Social Security was 70 years ago.
But it's not a slippery slope to socialism, but rather a slippery slope to a further invalidation of their most cherished beliefs.