With Yamato's introduction, I'm now positive nobody will be joining for a while. Oda is most likely setting up the new generation of leaders whose people will become part of the Grand Fleet: Carrot will lead the Minks division, Karakuri the BM one, Yamato the Beast Pirates one. This to be joined at a later stage by Smoker leading the Reformed Marines, and Sabo leading the Soft Revolutionaries (I believe Dragon's brand of revolution has too high a cost in terms of human lives, which is why he will never succeed, but that's a whole other discussion). I'm uncertain as to whether or not representatives of the remaining Yonko (excluding BB, of course) will also form a similar relationship to the Fleet–maybe a Rockstar or Rockstar-wannabe for Shanks, and Marco for Whitebeard (though, given the WB Pirates' involvement in the current arc, and the Weevil plotline left open for future conflict, they might be taken out of the equation soon).
This kind of speculation opens, of course, to questions as to whom will also aid the Fleet from the Paradise (Vivi is a given, but will the Skypieans play any role, or is Enel alone set to return?) as well as from the remaining islands of the New World--we have Hajrudin as the token Erbafian, and Scooper might play a bigger role than Rayleigh (perhaps in relations to the God Valley), though as the moment airying theories based on nothing is moot.
But returning to the potential nakama main topic, like I said, I don't believe anybody will join for now. The aforementioned "candidates" for stated reasons, and Tama because she's thoroughly linked to Wano. A while back there was a theory linking her to Orochi on grounds of their unique hair color. They might indeed both belong to the same, time-and-again discriminated clan. And since this arc aims to show the Wano people how their mindset in regards to geopolitics and racism is outdated, it'd make sense for Wano to have a double-regency by the time Kaido is kicked out and Orochi imprisoned. A double regency in the guise of Momo and Tama, the bloodline of the royals and the bloodline of those who had been persecuted for no fault of their own other than being born from this woman rather than that.
The Scabbards are, likewise, Wano material, whose destiny is to help the country transition toward the ideal Oden had in mind.
The Supernovas are... Supernovas, each with their own crew, meaning they do not, imo, even belong to this poll.
And it's pointless wasting characters on someone like Caribou, who's the polar opposite to the SHs.
So for want of dishing out arbitrary percentages as to the nakama likeability (and in spite of the fact that, yes, I had voted for Yamato at the time her introductory chapter came out), I have it at a flat 0% that nobody from the current roster of "candidates" will ever be Strawhat material.
