I can see both Carrot and Yamato joining no problem. Yamato cause of obvious Oden parallels. Carrot because she’s been around since Zou, played a role in WCI and I can’t imagine why Oda would give her that much screen time if otherwise. Carrot also featured in a SH heavy panel celebrating the return of Jimbei. Carrot will join kinda like how Franky did, as an ally and later nakama. Plus 2 new female crew mates wouldn’t hurt.
I’ve also seen people mention Momo and Tama as potential nakama. But I don’t see it, I’ll admit I’m biased though. Don’t like Momo for reasons.
But I do look forward to his potential as the son of Oden and his DF power working in tandem with his potential swordsmanship.
People will cite Shanks and Buggy’s presence on Roger’s ship as apprentices as proof for Momo and Tama joining fullfilling a similar role. Due to the parallels seen between the Roger pirates and the SHs. But I’d argue that those are two different matters because it’s alluded to Shanks and Buggy possibly being on the crew since infancy.
They’d also argue that as Oden’s son he must learn the poneglyph cypher from Robin, because it’s his heritage. But Robin already fills the role that Oden did on Roger’s ship. Following the discovery of the One Piece and the upcoming Great War, whose to say that information will be needed post then.
I believe Momo is the New world equivalent of Vivi and as such his journey ends in Wano. As the future Shogun, and the future he represents for Wano, he needs to stay and mature into his position with the help of his vassals, and daimyo. That’s were I see Tama becoming Momo’s Shinobu or Fukurokuju. Both becoming allies of Luffy, nothing more and nothing less.