Well, I was one of the people that never saw Yamato as Nakama in potential. She was never written like one, so her not joining for a reason or another is understandable. Her destiny is probably help in the final war as a captain of what remained of the BP.
Carrot is, in my opinion, not written as a Nakama and SH but, at the same time, she seem to have the potential to travel alongside them for a while before growing as her own character. So I can see her travelling with them for a time to grow as a leader and leave the crew later like Vivi.
Vivi is also a weird case. She is Nakama but, at the same time, she seems to be written like a non-permanent member. Someone that will join to solve her own issues and leave later, instead of keeping together with the crew. While I would love to see her again I don't think she is the final Nakama.
At the moment, Tama is, for me, the one that is better written to be a nakama. The fact that she was delayed because she lacks offensive potential adds to her Nakama points and is incredible similar to Jinbe. Considering that she was hinted since pre-ts, her connection to the crew and her backstory I would love her to join later, but I don't know if it will be in time to have adventures or just joining to fulfill the promise at the last minute.