I also agree with the Fire/Rock prediction.  I'm kinda hoping for something like Leviamon, but with rocky crags instead of the blue fins and fringes, and flames from the nostrils, instead of steam/smoke.  Obviously done in Pokemon's cuter art style.
[img]https://vignette.wikia.nocookie.net/kingdom-hearts-unlimited/images/8/8e/Leviamon.png/revision/latest?cb=20190717195639[/img]