One Piece thread (Spoilers)

They could always go with the "Will of D" being the reason that someone could eat more than one fruit.

Still, if someone allied with Luffy does *have* to eat it, we can already rule out Brook, Robin, Chopper, Kinemon, Momonosuke and probably Luffy, because they already have fruit abilities.
Of the remaining major allies, Zoro, Sanji, Franky, Nami, Ussop and Jinbei, I don't think that Jinbei would want a fruit (Losing the ability to swim would be terrible for him) and Zoro doesn't seem like the kind of person to really want a fruit ability, nor does Franky. That leaves Nami, Ussop or Sanji. And honestly, neither Ussop nor Nami could do the Mera mera fruit justice (If one of them gets it, it would have to be played for laughs...).

So I think Sanji would be the most likely to end up eating as it would suit his fighting style and current abilities more than anyone else currently allied with luffy.

Read a theory on some other forum that stated that Luffy would get the fruit, hide it and protect it, then, after he became the pirate king, would give it to a kid that he would see that resembled Ace and him when they were younger. I think it's a very poetic end for One Piece, but i don't think Oda is going to do that any time soon.