If he had sold out on the round 2 uppercut or something, it could have happened...I guess. Still unlikely of course - he was pacing himself and not going for KO punches so he would have had to know that was going to be there (and not even clear how much power he had with boxing gloves on).
I think he would have rematched Floyd and lost on the rematch, then had a rubber match and retire with billionz. If somehow he beat Floyd twice there's no way he would ever fight MMA again - he would probably have taken on a top young gun in boxing and gotten brutalized, but for a giant PPV - and then retire.