We already had the training arc with Rayleigh, so there's no need to repeat the exact same thing. But it is true that Luffy is going to need a guide to awaken his df. So it's probably not gonna be the training like with Rayleigh, but more like having someone to guide Luffy.
There's very little to know about Yamato as of now, so I don't really know what to say about him. He did say he was waiting for Luffy but...I need to know more. But if someone's going to be guiding Luffy through the awakening, I'd prefer it to be someone else I think.
I also have a feeling that oda would probably kill someone off, not gonna bet who its going to be but ..not many impact full choices
Lol yeah I also think someone might die, not now, but in the future. Maybe at the end of Wano war, or a future battle? Since it looks like Wano is going to turn into a massive war, I'm going to assume there'd be some heavy casualties. but Oda better leave Marco alone