Back in Punk Hazard Luffy declared he wanted to defeat all of the Yonkos. But by now it’s pretty clear that they’re just gonna escape without defeating Big Mom herself. Katakuri asked if Luffy will return someday to defeat her and he said yes. But I don’t think he’ll get the chance.
Here’s what I think will happen: after the Straw Hats escape, Blackbeard, upon hearing the news of what happened on Whole Cake Island, will take the opportunity to take down Big Mom because of the general weakened state of her crew after this whole mess with the Strawhats/Firetank/Germa 66. But isn’t Blackbeard moving to attack the Revolutionaries right now? Yeah, but honestly I think it’s too soon for those two groups to have a real clash and have one of the two completely defeated. My guess is that the Revolutionaries will somehow manage to learn that the Blackbeard Pirates are on their way and flee their base. Not because they’re cowards but because fighting a freaking Yonko crews is not their goal at the moment. So I think Big Mom will be eliminated from the race by Blackbeard.
Kaido will eventually be eliminated from the game by the Strawhat Alliance.
As for Shanks… it’s hard to tell.
I used to think Blackbeard would defeat him. But now that I think Blackbeard will defeat Big Mom… I don’t know. Will he defeat both of them? Maybe. And if he doesn’t, will Luffy himself fight Shanks? Will Shanks actually want to fight Luffy? Probably not… anything regarding Shanks is the hardest part of this series to try to make any predictions.
What about the other Supernovas?
I think they’re whole point in the story was never to be antagonists. I think at some point all of them will be allies to Luffy. Kidd is most likely gonna join the alliance in Wano.
*Theory by sameljota