Most 'out there/left field' movie for him to do next
Totally defying expectations enough to make ppl think the announcement must be from a parody new account (https://twitter.com/DisbussingFilm) and more than if he did say Bond 26 or The Dark Knight Returns as although it'd be surprising it'd be not totally shocking/unexpected like:
Avengers Secret Wars
Fast & Furious reboot
Star Trek (either a 4th Kelvin movie or a new reboot)
Terminator 7
Inception 2 or Interstellar 2
The Ken Movie