My preference is to fire him now. I also agree that if he wins 10 games next year, keeping would have been proven to be the right move.
I also believe this will be the only mulligan season BK gets at ND. The problem is: what counts as a mulligan to JS? I suspect if Kelly is brought back and he wins 9 games, he will certainly be retained. 8 wins? That might even be enough. I think its safe to say that less than 8 wins and he gets the ax. The problem is the 8-9 win range, which is probably good enough for Kelly to keep his job, but just delays the inevitable as he enters yet another year on the hot seat.