Considering InTrade has Obama being re-elected at 53.9%, I think the credibility of that system is quite suspect .....
“The US Supreme Court to rule individual mandate unconstitutional before midnight ET 31 Dec 2012 (78.2% Chance)”
57% of former SC law clerks also think the mandate will be turned down. http://www.washingtonpost.com/blogs/ezra-klein/post/poll-former-supreme-court-clerks-think-the-mandate-is-done-for/2012/06/21/gJQAYn8ZtV_blog.html
Likewise, 57% of SCOTUS-watchers at FantasySCOTUS predict the mandate will be turned down. http://www.fantasyscotus.net/healthcare-case-predictions/ This latter group bats around .600 in making predictions about SCOTUS. Note that only 1/3 believe the mandate is not severable, i.e., that if the mandate goes, everything will be struck down.
Thus, the most likely outcome is that part(s) of the law will be voided, leaving the rest of the ugly mess behind. Republicans will need to do the rest of the heavy lifting when it comes to eradicating this turkey.