There is no post-credits scene in Gladiator 2, so you don’t need to wait after the credits roll. Fans of the film can exit once the movie ends without missing any additional content.
As for a potential third movie, while there’s no confirmation yet, Ridley Scott has previously mentioned ideas for further sequels in the Gladiator franchise, though a follow-up would likely depend on the success of this installment. Keep an eye out for any official announcements as the sequel continues to generate interest.