By upholding Obamacare, the Chief Justice has given Republicans a legal framework to support privatizing Social Security and Medicare.
Many are saying Chief Justice Robert's decision to sustain Obamacare was designed to preserve the long-term political capital of the Court. I think he simply made the decision he ultimately decided was right on the tax issue, which the precedent strongly supported. But to the extent a long-term political angle may have subconsciously motivated him, there is a large one that commentators have so far missed.
The unseen long game is that sustaining Obamacare as a tax helps preserve the Republicans' ability to adopt two items on their own political wish list: the Paul Ryan plan to privatize Medicare and George W. Bush's plan to privatize Social Security.
Consider the Ryan plan. It would convert Medicare into a voucher that seniors could use toward buying medical insurance from either Medicare or private insurers. The voucher amount would equal the cost of the second-cheapest plan, so if traditional Medicare is not one of the two cheapest plans, individuals would have to buy a private plan to avoid paying extra.
In short, under the Ryan plan, Medicare would become a mandate to make contributions into a Medicare trust that you would later draw from to buy yourself medical insurance, which could be from a private insurer, and might have to be so in order to avoid paying a penalty. This looks a lot like Obamacare's mandate to buy yourself medical insurance. There are two seeming differences, but neither is telling.