I agree with Howard Dean: It would be better for everyone if the court nixes the individual healthcare mandate. It smacks me as being unconstitutional and always has. Plus many on the Left are correct to assert that the end of the mandate would create a rallying cry for a single payer system once and for all.
Single payer would, of course, be essentially impossible to pass at this point. (Obama had the chance in 2009 with Dem majorities in both houses but, alas, he caved at the behest of insurance companies.) This difficulty is beside the point, though. The Left itself should never have cravenly signed onto Obamacare. If the mandate goes down a concerted push for single payer would return a smidge of principle to the Obama-era Left.