I'm sure I'm in the minority but I don't think Yama will join the crew but probably the fleet as the representative of Wano for Luffy's fleet.
There have been a lot of little things and Jinbei's line this chapter adds on.
Notice how she's still giving orders to the Beast Pirates remnants and they're listening to her.
With Kaido beaten, possibly dead though unlikely, and Luffy leaving are the Scabbards and samurai strong enough to keep the WG out without the strength of someone like Yamato?
Her fruit is described as the guardian deity of Wano calling back to my last point.
Luffy's had multiple interactions and chances to invite Yamato into the crew but he hasn't yet. Doesn't that seem odd, Luffy's never hesitated to ask someone to join if he wanted them to but he didn't ask Yamato even as she was explaining her situation in the attic.
There have been a lot of people, even before this chapter, that were on the fence about Yamato joining. Though, the reality is that in the very least there is absolutely nothing that holds her back from joining.
Fleet representative? For us it's an important distinction whether a character truly becomes part of the crew or just tags along for a while, but that does not apply to the people in the OP world. At this stage of the story if someone joins the crew, regardless of the motivation, it pretty much is till the end. So, this 'fleet representative' thing is kind of redundant, unless you're saying she will remain behind, similar to how Bartolomeo & co do their own things, however that would have made this entire issue pointless. Then there would have been no reason to bring it up at all.
Jinbei just plainly stated a fact; that in the end it's the captain that decides, which is a very Jinbei thing to say. When he was first introduced in ID, he made it very clear he isn't a nice person that's just going to help anyone who needs help. For him this is simple: if Luffy says ok, it's ok for him, if Luffy says no, Yamato can go piss off. This is a reflection of his personality, just like how the reactions of the other Strawhats were reflections of theirs. You can't really single out Jinbei's reaction, while in that same scene Brook, Sanji and Robin were not apprehensive about Yamato.
The entire chain of command of the Beast Pirates is gone: Kaidou, the three Calamities, the Flying Six...Yamato is pretty much the only one left they are familiar with, but it has been a regular occurrence during this arc that many are confused with her orders as they benefit the enemy. Many are still not entirely aware that Yamato fought against her own father.
Wano was able to remain isolated for centuries. On top of that they have the support of the Mink tribe and possibly a bit of the remaining WB Pirates. If push comes to shove, they can also borrow the Strawhat flag. Even though Yamato is strong, if the WG really wants Wano, her presence there isn't going to make much of a difference.
This whole guardian deity business can just as easily be interpreted in a completely opposite manner, namely that to protect Wano she has to go. Yamato wants to make Oden's ambition a reality and for that she firmly believes she has to leave. Why? Because of what Oden wrote himself.
All the interactions Luffy had with Yamato, were during the raid when they were almost always fighting. Even Luffy, as aloof as he is, isn't going to start recruiting people at such moments. This is absolutely not odd. In fact, if anything, the moment he truly tends to ask people would be...right now.
The truth is simply that there are absolutely zero reasons as why Yamato would have to stay in Wano. As much as I've become fond of her character, it remains a fact that she was introduced relatively late and came out of the blue to the point it really feels like it was a list minute addition and that she had to be retroactively fit in the established narrative. Not only is she strong, but she's also in the possession of what might be one of the most important documents in the world (Oden's log) and based on that she adamantly believes she has to leave Wano and join the Strawhats.
What would have been the point of her character if she remains in Wano? Despite the fact that she spent most of her life there and admires Wano, its culture and the Kozuki clan, she was never one of them. Momo can't leave. The Scabbards are never going to leave Momo alone. Tama is too young and Komurasaki isn't a fighter. Who is left then to bring Oden's ambition a reality? Yamato, in particular because she is expendable. Her whole character seems to have been written purely for that specific purpose. Without it, what merit was there in adding her to the story?
I get the feeling many people are against Yamato joining exactly because she came out of nowhere and then explicitly claimed what might be the last spot in the Strawhat crew. Normally, people debate for years about new Strawhats and then suddenly Yamato swoops down.