Well, 75% of his justices he appoints will find RomneyCare unconstitutional!
I was reading Roberts opinion on the decision, and he clearly differentiated between what the state can do in these situations and the federal governments reach of power. In fact he drew so many distinctions between state and federal power,that it gives me the impression Romneycare would be found constitutional, regardless of whether it was stated as a tax or a mandate.
Why would that matter to Alito, Scalia, and Thomas? And there was that recent Montana campaign finance case that had the same 5-4 split that Citizen's United did.