You're all hyping up Dragon Yamato, but he's not going to end up a dragon, he's going to end up looking like this:
The whole shadowed form concept is almost always met with a gag in one piece fashion. (edited bag to what I meant to say: gag)
Why that picture though? Well that's a White Plover, and why would I say he's going to be a White Plover zoan user? Because that's what Yamato Takeru (the mythological inspiration for Oden and Yamato himself) turned into when he died, well his soul, before it flew away.
He's going to have the Tori Tori no Mi: Model White Plover.
His teeth are probably something to do with the actual race that Kaidou is, and in the end of the day, Yamato's devil fruit is going to allow him to fly: yes, but it's also going to just be a joke reference to the story of Yamato Takeru.