I voted "No". From a story standpoint Ener did go crazy and will probably not be fit to be any trouble for anybody. If he does come back it may be in a first page serialization, like the others.

From a writer's standpoint, having someone with Eneru's powers would be tough to work with over a long period in terms of balancing the plot with the protagonist. Luffy is probably his only weakness and to bring him back and be defeatable would be repetative.

I too have questioned how characters like Smoker are going to be beaten, but Oda has a done a good job balancing weaknesses and probably not put himself in a position where he would "lose control" of his characters to the point where it becomes rediculous. Could anyone else but Zoro have actually beaten Mr. 1? Among the protagonists of that time, I don't think so.

Getting back to the actual question, here's something else to think about (if it's been mentioned too much before, I apologize): So far all the Shichibukai have had animalistic names:
Jinbei (whale shark)
Juraquile Mihawk
Donquixote Doflamingo
Bartholomew Kuma (bear)

By this pattern, Monkey D. Luffy is more likely to become the next Shichibukai. However I think if he was ever offered the position he would shove it back into the Government's face