@Zarnikon:
Luffy wasn't weak before the timeskip, he was strong and fast.
During the time skip he trained with one of the strongest men alive. So he mostlikely got even stronger (physically) and he mastered haki. Why do I say that he mastered it, because of the following:
In chapter 597, page 16 rayleigh explains the CoC and I quote: "You must not use it until you can completely control it. Otherwise it'll intimidate innocent people around you aswell…!!"
Now in this chapter we saw luffy using it and he did not affect anyone innocent, he focused it on all of the Fake SH's and no innocent people were intimidated. Now I would say that CoC is probably the hardest one to master, and Luffy mostlikely also can use the other 2 haki's really well.
Now you ask what could have happend during the TS making him even to an admiral.
We all agree that luffy isn't even to an admiral but he should atleast form a threat and be able to stall thim.
@brennen.exe:
Luffy has always had the other tools. Creativity, fighting skill, raw physical strength, experience; all he lacked was exactly what Haki provides him with. From this point on, it should only be experience that really elevates their power. I'm not saying his other stats won't increase a little here and there as the journey continues, but it shouldn't be significant growth like it was during the Grand Line. Experience should be the only thing left, allowing him to further master all applications of Haki. The earlier portions of the story were eye-opening for the crew, forcing them to learn just how small they are and spur their desire to gain strength. This time-skip was the answer to that, giving them the perfect opportunity for isolated training in the perfect circumstances. If two solid years of that cannot give a solid base for them to stand on in the New World, then nothing can. Put it this way, there is no longer any reason for Luffy, at any point hereafter, to have another sudden boost in power due to need; were there a need, then Rayleigh's training would have been unsuccessful, and the timeskip would have failed to serve a real purpose in that regard. So again, any growth from this point on should be gradual, building more off of experience than anything else, and providing only minor growth, relative to their journey as a whole. IE: On par with or above Vice Admiral yet below Admiral, to above Admiral or on par with the strongest people in the world.
@brennen.exe:
Well then you aren't really agreeing with me, since that misses the point completely. The purpose of the time-skip, for the crew, was because they weren't prepared for the New World; Rayleigh's words were, "do you want to repeat that?" referring to the incident at Saboady. If Luffy– having devoted an entire two years to pursuing that same goal, with the perfect teacher and circumstances no less-- if he runs into anything from this point on that requires him to reflect on his own powerlessness and seek more power in turn, then the time-skip would have failed to do exactly what it set out to do. Of course as he is now he needs to get stronger, arguably 'a lot' stronger, but he should already have that base for which his steady growth will stand on. Think East Blue.
So… I had to quote a lot of people here seeing as they are the bases of my argument... Firstly I think the misunderstanding people are having is that they think the below people are saying Luffy & Co aren't going to grow. And it seems to me what these people are saying seems exactly right... Luffy & Co now have the foundation to crew to whatever heights their potential can take them. Were as the first half of the grandline they were relying on mostly 'natural talent' and some rudimentary skills to get by. Yes I know a lot of them had 'training' but I'm saying that they are all still young and compared to people who have spent their entire lives improving its hard for a group who has only been pushing forward for 6 months to compete. What the TS did was give them a foundation a building block to greatness...
Okay, Next argument... Luffy isn't a genius... However his battle sense/tactical reasoning borders on prodigious... Proof? The fact that after only seeing the Roukishi technique once he made a suitable copy of the move based on his Devil Fruit power... Not to mention he did this while he was getting his ass kicked to kingdom come... So your argument about 20-22 years of experience is bleh... I mean every single opponent Luffy has faced has had more experience and more time to develop their strength yet they still lost... Luffy says it all the time and I'll say it again... 'Then I'll exceed you...' Overall years of experience matter little in One Piece world...
COQ argument and why Whitebeard didn't use it... COQ as stated by Rayleigh varies in power depending on the 'Will/Belief' of the user. Which means there is a very good chance that Whitebeards COQ was out of range of the execution platform... Luffy was far closer the the execution platform and thus his COQ was in ranged when he used it.
Final argument... Luffy is not on 'Admiral' level... But could he slow one down? Most probably... Could he escape from one barring any unforeseen circumstances/problems. Most likely... The whole point of the TS was to make sure that in the future they wouldn't be completely out classed... Not to say that they wont have tough battles ahead but the TS purposes was to simply although them to take on 'the top'... To pretty much make sure that they could limit the amount of situations that left them utterly powerless... As they go from now on they will exceed their opponents were in the past they had to often struggle to survive. There will be power-ups, there will be new skills learned there will be defeat in their futures but never again will they be incapable of lifting a finger in their own defense...
Sorry for the really long post...