As you all know Dressrosa is reaching its climax and there are many ways the final fight will play out. I feel that luffy will face doffy on his own and the reason simply being due to laws injury which will balance his power with that of trebol. Next, Bellamy will play a big part in motivating luffy into getting that extra willpower to defeat doffy. furthermore, it was stated that luffy is the trump card (Rebecca asking his help). all in all luffy will definitely face doffy on his own due to one reason or the other.