Of course, as we know since the first episodes, in the world of One Piece Devil Fruits are extremely rare things which can make people extremely powerful once they eat them; in exchange for this power, the Devil Fruit eaters aren’t able to swim anymore and they’re weak against seastones.
Going on with the story, a lot of fans speculated that, before the big fight against Kaido and his crew, the Mugiwaras will find a Devil Fruit and one of them will eat it, making the crew becoming even stronger. In addition, we also know that, among the Mugiwaras, some members already own some Devil Fruit powers: Luffy, Chopper, Nico Robin and Brook; for this reason, they couldn’t eat another Devil Fruit, since we know that if someone who has already eaten a Devil Fruit eats another one, then they die.
Considering now the remaining members of the Mugiwaras, I’m convinced that will be Zoro the one who eats the new Devil Fruit. Why? Well, because he’s the crew first mate and he’s also the strongest one after Luffy, so he supposedly needs some more power.
In fact, I believe that Sanji is not made for being a Devil Fruit user because, for example, if he becomes not able to swim anymore, he couldn’t save Nico Robin if she falls in the sea water; furthermore, Franky is a cyborg, so I don’t think that a Devil Fruit would fit with him, Nami shouldn’t really need it, since her duty isn’t the one to fight, Usopp should become an Observation Haki master rather than a Devil Fruit user and Jinbei is a fishman, so eating a Devil Fruit would mean for him not being able to go underwater anymore.
Moreover, as far as what could be the found Devil Fruit, I thought of two main possibilities: the first one is the Sala Sala no Mi, which had been eaten by Smiley (Caesar’s “pet”), while the other one would be the Yuki Yuki no Mi, which had been eaten by Monet.