Proposals to enact a private mandate with some subsidies for the poor in order to spread out health care costs from Bob Dole to Mitt Romney and eventually Barack Obama aren't new. Richard Nixon was the first to propose such an idea. Requiring everybody to purchase privately-run health insurance policies has been floating around the Republican Party for decades as a center-right alternative to LBJ's Medicare or Harry Truman's national health insurance fund, which in modern terms was basically a "robust" public option to compete with private insurance only without the mandate to purchase insurance.
What's destabilizing the health insurance market is skyrocketing health care costs in the face of stagnant wages, and the bill Obama signed doesn't really have an answer for this problem, because such an answer would've been dead on arrival in the Senate. Yeah, you might get a two percent raise a year as a "cost of living" increase from your employer in your non-union workplace, but if the real inflation rate is five percent or higher, guess what your insurance company is going to charge you. It is conceivable that if this trend continues, a huge chunk of the United States, sooner or later, will be in a position where they're forced by law to carry private insurance policies that they literally can't afford to use because the deductibles and co-pays would bankrupt them, yet they still make "too much" money for any federal subsidies to kick in.