As you can see here, Joaquin Phoenix seems to not know of any Joker sequel plans. Having made $1,074,419,384 on a budget of $70,000,000, the film was enjoyed by many fans and has had sequels rumored since its release.
If an announcement were to occur about a sequel soon, my guess would be that it'd be at DC FanDome 2021, which begins on October 16, 2021 at 10:00 A.M., Pacific Time.
