The early reports of argument suggest that the Court is sort of all over the place on the matter of severability. Paul Clement received lots of skeptical questioning, across the ideological spectrum, for his contention that the entire ACA should be void if the minimum coverage provision is unconstitutional. But Ed Kneedler is getting tough questioning as well; the conservative justices wonder how exactly they are to determine which of the hundreds of provisions should stay and go. Reports are indicating, though, that there seems to be a consensus (with the possible exception of Sotomayor) that the guarantee-issue and community-rating provisions must fall if the minimum coverage provision go down.
The fact that the Court is this engaged on severability cannot be a good sign for the Government as to the constitutionality of the individual mandate.
SCOTUSblog has updates here and here.