Really amazing point, this actually may be her correcting Oden's mistakes, not leaving Wano unprotected, and joining later,
^That's the point, I think Oda is purposely having her being the "better" version of Oden by not repeating his mistake and I don't see her leaving the Guardian job until Momo masters his fruit, which I don't think is happening before the final war. So Yamato will technically join at some point but I'm not sure the fans will actually get the occasion to *enjoy* it. Like, Tama was also promised a place (and is even training seen training for it in the cover story) but she clearly isn't joining before the epilogue.
Oda is partially to blame for his nakama baiting, but it doesn't seem Yamato is unhappy on Wano. I've seen her fans complaint about how it's unjust for her to have to give up on her dream but it's more of a postponement and actually exploring Wano / interacting with the locals does count as an adventure.
I've actually predicted her staying on Wano because of this fight against Kaido and her having much more interactions/development with Momo than the rest and it got me a lot of insults for being "in denial" lol.