According to reports, Carroll is staying with the Seahawks on an advisory role, but I personally don't buy it myself. I don't think Carroll would want that though, to be kicked to the curb and stay on the organization that threw him away rather than let him retire gracefully. I think Carroll fully retires.
Belichick on the other hand is an interesting one. It'd be his chance to prove himself like Tom Brady that he can win a Super Bowl on a different team. None of the teams that are available rn are exactly the most interesting picks outside of maybe the Titans and Falcons.