User blog comment:Rdolfoa/Top 3 Realistic One Piece Theories/@comment-24850639-20160908195210

Not really a theory at this point, Sanji being stronger is practically a given. Remember this is a manga though. Its all black and white until we see it in the anime, so there has to be more to the story than just new flame color, since that's not really something we'll be able to notice like that. If the only real meaning behind the blue flames is that they burn hotter, there's all kinds of different ways to express that. Not that it can't still be a new color (they made Poele a Frire have a white/pinkish tint to it in Fishman Island), but I'm moreso expecting to see a greater mastery of the flames themselves if anything. Maybe he'll be able to create whole rooms made of fire (Hell's Kitchen blah blah blah) or manifest animals and spirits kinda like Zoro. Also don't forget he has Buso Haki that we haven't seen yet, wouldn't surprise me at all to see him work that in somehow.

Kaido pretty much stated my sentiments on the other two. I was a big fan of the Marco-Red Hair theory for a while, but the NekoMamushi revelation changed that. We can't assume anyone's intentions of course, but I'd imagine that Shanks probably wants no exposure to the limelight whatsoever when it comes to the Kaido war. He can't have his proud dad moment when its all said and done if he helped Luffy along the way. I also don't see any reason for him to squabble with Weevil. He respected WB and his crew, but lending his assistance to take out one guy badmouthing the crew seems a little overboard. If Marco does join the Red Hair Pirates, it would have to be after the Kaido/Weevil situation is resolved. As far as Kuzan goes, we don't have enough to even speculate really. We know absolutely nothing about the situation whatsoever, and we know too little about Kuzan to really make any good guesses as to what his plan/motivation is. This could be him acting on a personal grudge, or he could actually be an evil dude for all we know.