As far as I'm aware, we have only a few indications towards it.
It's a carnivorous Zoan with pronounced canines:
It's
epic:
Sasaki was initially affronted that Yamato thought she could defeat him while protecting dead weight:
However, once she hinted that she might transform, he was terrified:
Yamato's Devil Fruit was likely provided to her by Kaido (seeing as she's been a prisoner on Onigashima since she was 8 years old):
Kaido intends to make Yamato Shogun:
Given that Kaido has such high ambitions for her and that he also trained her (she can perfectly replicate his signature technique):
We can thus surmise that it's a pretty powerful and rare fruit — the best Zoan that Kaido could procure. This lends real credence to the hypothesis that it could be a Mythical Zoan (or at least a
very powerful Ancient Zoan). Whichevet it is, it should be a fruit that's
considerably more powerful than what any of the Tobi Roppo or Calamities have.
I don't think an Ancient Zoan is likely as what I would expect to be the most fitting Ancient Zoan for the teeth profile we got (Smilodon) has already been taken by Who's Who:
A Dire Wolf might fit the pronounced canines, but I don't think it's "epic" enough.
I don't think dinosaurs fit the teeth profile we got.
Another reason to be sceptical that Yamato's Devil Fruit is a mere Ancient Zoan is how secretive Oda has been with it.
It's been 30 chapters since Yamato first appeared on panel (983) and 7 chapters since Oda teased her Devil Fruit (996). We have seen the Devil Fruits of every other "executive" of the Beast Pirates. Oda seems to be saving Yamato's Devil Fruit for an epic reveal (presumably against Kaido). It's hard to imagine that a mere Ancient Zoan would warrant him being this coy.
Acting under the assumption that it's a Mythical Zoan, the
White Tiger (Byakko) seems to merit special attention:
In Chinese Mythology, it opposes the
Azure Dragon (Seiryu) and would signify
Yamato's conflict with Kaido.
For what it's worth, this is Yamato's colour scheme:
What do you guys think? Suggest more options for her DF. I'll add up to ten candidates to the poll.