I would not bet the farm that they will. In fact, if I was a betting man,I would bet that they find some excuse to uphold it.
I think the Illegal made a fatal error in his 2010 State of the Union Speech when he called out the Court for its decision in the Citizens United case. Justice Kennedy, the very man he needed most to persuade in the inevitably upcoming Obamacare case and the Court's most mercurial justice, wrote the Citizens United decision. Hence, the Illegal's attack on that decision was a direct, uncalled for attack on Kennedy himself. Add to that the Illegal's current, fanatical, attack on the Catholic Church for defending its most basic doctrine, with Kennedy being a Catholic, and you have a perfect recipe for Kennedy playing, "don't get mad, get even."
Indeed, even if Kennedy cast an initial, preliminary vote in favor of Obamacare, I suspect the Illegal's most recent ignorant and inflammatory diatribe against the Court might cause Kennedy to change his vote. Hence, my guarded optimism.