Personal viewpoint I think adding other creatures especially something fantasy ones like dragons, would completely ruin the atmosphere that FH have right now, it wouldn't blend aswell unless you were focused on making it like that from the start.
Will always think that Felines and canines will be enough in FH. If there was other creatures to "hunt", that would be fine. But playing around as them aswell wouldn't be.
Especially since it would probably require work to make something like that possible, and I'd rather see the game grow and become more functional gameplay wise like IT was with all the actions and functions it had.