Underwood isn't likely to go anywhere for a while. He's staying after this year based on the incoming recruiting class. If we lose Ayo and add Hawkins, Curbelo and Miller and see some improvement, he'll keep his job beyond that based on promise. Now if Miller backs out or signs elsewhere, Ayo leaves and GB leaves (maybe to go play in Europe), and Kofi leaves and the rest of this season tanks, then things might be different. So who might be available? IDK- this job is like the football job. With each new coach and each bad run, the job gets less appealing. Weber recruited poorly and then when he recruited well, he couldn't get them to play together. Groce was poor recruiting and coaching. Underwood seems to have a good eye for talent, be able to at least employ assistant coaches that can recruit but something strategy-wise or preparation wise or coaching wise or chemistry wise is missing for sure.
As far as names that might be considered...
I think an obvious candidate and likely taker would be Steve Henson. He's winning at Texas-San Antonio and would have a Lon Kruger endorsement.
I would like Anthony Grant but he seems to have things rolling at Dayton and that's his alma mater. Depending on who you believe, Grant has had chances to accept a job here and declined interest. I'd also like Jared Haase from Stanford but I can't imagine he'd leave his situation at Stanford especially since he is from California.
Other names that come to mind would be Ben Jacobsen at UNI, maybe Brian Wardle with his success at Bradley. Some names to really consider IMO- Johnny Dawkins(UCF), James Jones (Yale), TJ Otzelberger (UNLV- things aren't going great there so far but TJ is a good coach and recruiter and would do very well back in the Midwest) Damon Stoudamire (has Pacific winning again), Baker Dunleavy (a Jay Wright guy doing well in his time at Quinnipiac but more of an east coast guy obviously), Ronald Nored (Midwest roots, Brad Stevens guy, NBA Hornets).
A wild card? Maybe Shaka Smart is looking to hit the eject button.