All the Justices do. The case will be argued next February or March, when all of us will have a better idea of whether President Obama will be reëlected. If Obama looks like a lame duck at that point, it will be a lot easier for the Justices to dismantle his signal achievement; if Obama looks like a winner, some on the Court may think twice about picking this particular fight with him.
Jeff Toobin posits that “this case, like any big case, will be about power.”
It all goes to show that sometimes (often) you don’t need a law degree to know how the Supreme Court is going to vote—just know which way the wind is blowing.