Looks like Gregory Garre is the new SG:
http://www.scotusblog.com/wp/court-notes-sgs-service/
Garre has almost an identical resume to Chief Justice Roberts; he was a clerk to Chief Justice Rehnquist, head of the Supreme Court Appellate Practice at Hogan & Hartson, and has recently worked as Deputy Solicitor General.
I don't think his elevation was too big a surprise; from what I've read, he's a tremendous oral advocate, and should do an excellent job in his new post.
Apparently Clement has accepted a faculty position at Georgetown Law for the upcoming year, so he'll be putting off any decisions as far as private practice.