I have to disagree with most of you guys on the smoker part.
Luffy never actually fought with smoker seriously, you can't say he lost.
He has no reason to. Luffy doesn't fight people because they are just marines, he fights them for a reason. Smoker was more then decent to him, never hurt his friends or did something unjust. Not only did luffy not fight him he even rescued his life.
So I am not saying luffy is stronger then smoker, but you can't say luffy lost or got owned, Luffy never really tried fighting, he just wants to get away from smoker everytime so he can continue his quest, he has nothing against him.
Luffy is always at his strongest when he is truly pissed and has a purpose.
Same reason he lost to lucci at the beginning since he was unsure of what robin was up to.
I think that if Luffy was to really fight smoker or hina for that matter, with full power and be really pissed at him, smoker will lose, since luffy now is really one of the strongest characters in the one piece universe.
But AoKiji is still stronger, and luffy will have to progress a bit more with each fight untill he can get to the level of the best(he's close now).
Also don't forget that since first meeting smoker luffy had countless battles risking his life all the time, he's much stronger now. I don't see smoker fighting with risky strong people all the time.
As for the next arc, I really hope it will be blackbeard and ace, so we can learn more about whitebeard and everything that happened.
If not doflamingo or arlong's boss jimbei. There are still so many enemies to cover even without new ones.
I also think luffy will fight one of the other emperors, not shanks or whitebeard. Since after he enters the 2nd part of grandline, he will probably do something stupid that will make that emperor really pissed at him, they will fight and the strawhat crew will win.