Imagine One Piece doing something like Boruto or how Dragon ball's done with gohan and trunks (gotena nd co). I'd put my son on anime just to continue lmao
You can bet your ass there will be somekind of spin-off when it's done.
Look at Goku, i love DBZ, but how long ago did it really stop being relevant ? Probably after Dragonball Z. Then they did GT and movies and super. It's being kept artificially alive and rides the nostalgia wave.
Naruto is another golden goose egg in the Toei/shounen basket, and One Piece is the golden goose itself, they will be selling cute chopper merch in Japan till the sun dies out.