I tried my best to make this post as cohesive as possible, but dang, to no avail.. it may come across as a sketchy read.. because it is.
1. Monkey D Dragon's ability:
In my opinion, a wind logia would suck. I mean what is wind anyway? it's the movement of gas (air: which is a mixture of gases), which is already everywhere. So Dragon, if indeed a wind logia, would be able to disappear as a gust of wind in thin air (becoming invisible like Absalom?) It sounds ridiculous to me. A weather paramecia sounds far more plausible, or a paramecia which could affect air movement in an indirect way, like heating or pressure control. But still, wind powers in my opinion come close to whitebeard’s power, I mean besides blowing his enemies away, expect him to punch his enemies with air/shock waves, like whitebeard, destructive indeed.
2. Kaidou and Big Mam sitting in a tree:
I predict, from the sight of his subordinate whom Drake went against (which doesn't really imply anything, just gave me the idea), that Kaidou is some sort of super cyborg, and at his arc, we will learn about Dr. Vegapunk and the pacifista project, and possibly about how devil fruits came to being (which I am sure will end with “each devil fruit will end up being eaten by someone who deserves its power the most”. Like Teach said: This power chose me Ace) But explaining the pacifista project means explaining Kuma’s involvement which means Dragon migh have something to do with the arc too. Kaidou’s technological abilities would go with perfect balance with a theory I came across earlier which said that Big mam's ability is controlling plant (and animal?) environments making her Big mother nature (you can't make this stuff up!). Sounds good, however the little amount of info we know about her, like her love for candy, does'nt support this in any way. More on that, maybe she doesnt want the candy to eat, maybe she wants it for another purpose, as in her jolly roger, which shows a tree that has the same shape as the fluff of hair behind the skull (which again supports the nature thing) shows the tree sprouting from the tip of a cane, which may as well be a candy cane!. Too ridiculous?? Look at what Franky does with cola. Nevermind these theories, what I can say is that it is highly likely that she will be the main villain in the fishman island arc, as from my perspective, Oda has already set up fishmen in general as a good race, and set up their bad apples (Hodi and Decken) as not strong enough foes to provide enough intensity against the straw-hats in the final battle, in which luffy would blast fishman island into smithereens, after that declaring himself its new protector. I am sure that jinbe is stronger than those two, and that he was surpassed not just by luffy, but also by zoro and sanji during the timeskip. This actually got me thinking that Jinbe being the next straw hat would not be the worst idea afterall, however I would prefer to see a fresh character like a young fishman or a human join the crew. A fishman will ease the rescue of submerged straw hat df users.. but then again.. Sanji's blue walk will also suffice.. do you think he can do that on land or air?