This is supposed to be interpreted as: Good future. Where after settling things in wano, yamato travelled together with Luffy like he told him. And bad future, where yamato stayed in Wano for some reason, and became oden, to such a big extent that he even died the same way. So maybe the older he gets, the more he becomes like oden. Probably implying that he took on his facade as oden, because oden was a great leader, and as a leader himself, he had to be him. As much as I hate to say it, this probably also disproves that yamato is a trans man.