The Momotaro tale already happened.
Again Oda won't straight up plagiarize a tale without making some heavy adaptations in the story.
You see, Momo whole purpose is to protect the land from the Oni demon, which he is already doing, the dog already helped by stalling the Oni demon until the monkey Luffytaro came back, Marco the pheasant hold off the Oni demons biggest threats until someone else could take care of them...
I mean we could still see Hiyori making some move as the pheasant but it almost certainly won't be something that game changing.
Oda is already doing the Momotaro tale since Tama (Kibi dango), Momo, Luffytaro (Monkey), Yamato (dog) and Marco or Hiyori (pheasant) will all have a part in the Oni demon fall.
It simply, it amazes me some of you guys expected the ending to be a rip off from the tale when Oda has already been making some heavy adaptations from the start with it.