I have no doubt Wicked will be coming to the parks somewhere, but I genuinely believe One Piece would fit IOA specifically the best of all the “rumoured” options.
I also believe even if the IP itself isn’t as well known as say Pokémon, to the American audience (even though I do think it likely is still very well known), it’s not always about selecting the biggest IP, but selecting one that would translate itself best to a themepark environment.
One Piece is about adventure, travelling the high seas, following your dream, all with a dash of whimsy, and fantasy. You can choose an island to base it on, build a market, sell devil fruits, create interactive experiences, and build some really cool rides, with some really cool effects.
Now that it’s been mentioned as something being tossed around, it’s where my mind goes for IOA.