I think we underestimate how stupid some NFL organizations are. LCE mentioned Raiders and I think that's honestly not a bad fit but O'Brien rubs a lot of people the wrong way and considering the whole Gruden thing...idk.
Teams potentially looking for HC next year: Raiders, Bears, Broncos, Jags, Lions.....maaaaaaybe Dolphins, Eagles, Giants.
Teams potentially looking for OC next year: All of the above + Steelers, Seahawks, Falcons, and others?
That's a lot of potential fits for O'Brien. Some with young QBs that are similar to Watson (Fields, Lawrence, Tua, Hurts). I wouldn't be surprised to see him back in the NFL next year.