I'm also not convinced that Scalia (and possibly Thomas, who's unreadable on this particular subject at the moment because of how profound his dereliction of duty habit gets during oral argument) won't find that the Anti-Injunction Act applies.
If I understand correctly, there are three issues:
1. They can't sue until the paying the penalty.
2. The mandate is unconstitutional.
3. The whole act is unconstitutional.
There might be a "moving majority" on all these issues.
For example:
#1. 1-8, with Thomas in the minority.
#2. 6-3, with Ginsburg, Sotomayor, and Kagan in the minority.
#3. 5-4, as Stevens casting the deciding vote.
I could easily see something like this (though not necessarily voting this way).
If the four "liberals" realize the mandate is going down but Thomas will vote to wait til 2015, why wouldn't they join him and live to fight another day?