Just adding my input here.
I listened to and read the entire day 2 and 3 oral arguments and I think the SC ruling the mandate unconstitutional is basically a forgone conclusion. To me it is very clear Kennedy and Roberts want no part of it. Kennedy also seems to lean in the direction of throwing out the entire law. But, I think the odds of that happening are a bit lower.
The ultimate irony would be if the SC tosses this on a party line vote just like the Dems passed it on a party line vote.