In Wano arc, We were introduced the Flying six a.k.a the Tobi Roppo.
We already know the devil fruits of 3 members till now and rest of the members’s devil fruits are yet to be revealed. X-Drake and Page One were introduced as Flying Six members. X-Drake has Dragon-Dragon Fruit, Ancient Model: Allosaurus and Page One has Dragon-Dragon Fruit, Ancient Model: Spinosaurus, in recent One Piece Chapter 983, Ulti’s devil fruit was also revealed, She has Dragon-Dragon Fruit, Ancient Model: Phychcephalosaurs.
As we know that , Beast pirates have Zoan type devil fruits, and It’s top commanders specially have ancient zoan devil fruits, we can expect Whoiswho might have Ancient Wild beast like Sabertooth kind of Zoan devil fruit,
Sasaki might have Ancient Arrhinoceratops kind of Zoan devl fruit,
and Last the Black maria might have there are two possibilities, She might have Python or Spiders devil fruit (by Bumber4472 on redit link http://gestyy.com/eqcwn4). There are less chances of her having Snake snake devil fruit as There are already Two snake snake devil fruits are there,Both of them are Sisters of Boa Hancock and Spider devil fruit user is not introduced yet in One piece.
We will come to know what Oda has in his mind in coming manga chapters. But still we can predict the possibility.