He most likely has a devil fruit considering his dream to create the strongest devil fruit user(and apparently zoans) crew, especially since he reached the sky island under unknown means to us yet. How did he reach that far without a flying capability?
And the flying zoan that seems more suitable to him is indeed the Dragon DF, which could also go in accordance to Kinemon's hatred towards the dragons demonstrated in Punk Hazard, but on the other side, Kinemon seems to particularily hate the Shogun more, so it could also be him and assuming Zoro do fight the shogun, it could re-create the dragon cutting scenario that Ryuma did in Oda's one shot and was rumored to have done in TB/Zoro did in Punk Hazard making it more ideal if he was the dragon devil fruit user instead
But it's true that with his introduction around reigning supreme even while under the sea, it makes you wonder if he really has a devil fruit, which would make his ambitions quite ironic indeed
Guess time will tell