Alright, so lets talk options. In no particular order:
1. Begin training under Mike Smith. I don't think anyone could argue that Mike Smith is one of top 3 best coaches in the US right now if not the best. His group has been very successful (Kincaid top American in 10K at Budapest, Luis 4th in 5K), and Grant knows Kincaid. Probably the most logical choice, since he'd get to keep his Nike contract and theoretically train anywhere he likes outside of occasional stints in Flag.
2. Sign with On and join OAC. On would have to be throwing a lot of weight around to pull the rug out from under Nike, but no other brand is putting that kind of money into sponsorships and no other established group has the pedigree of OAC. Ritzenhein likely has the most similar coaching style to Jerry, so it wouldn't be a huge transition training-wise. But again, very dependent on sponsor dollars.
3. Go bush league. Very Nice TC, Ben Thomas' group, or something of the like. Good groups in their own right, so calling them "bush league" might be harsh but they're not fully sponsored groups. This would also probably let him keep his Nike contract but again this option probably isn't quite as "pro" as he'd like to be. An athlete of his caliber needs structure and support that these groups don't have.
4. Wild card: NN Running Team. Someone else mentioned this but it wouldn't be completely unprecedented. Marc Scott joined NN after leaving Bowerman himself. They've got the money, they've got the structure, and they've got the swoosh. Maybe a more likely option than it seems.
So which will it be??