Shueisha won’t let One Piece end and money get away. I don’t think Oda himself will do any more work than the occasional one shot and designing video game and movie characters, but One Piece is going to continue. Videogames, movies, some dreadful One Piece Next Gen anime starring Shanks’ kid, manga drawn by his assistants, more spinoffs like the Ace one for popular characters, I’m expecting it all.
An outside bet is if Oda really wants to finish the series as soon as he can then he could probably cut half a year off the manga by having a canon Garp prequel movie.