At its best, the Batman Beyond movie would be a visual, cyberpunk spectacle wrapped around a compelling, noir narrative.
Batman Beyond can easily be handled that way.
And, needless to say, it could spawn numerous sequels, although obviously the creative team tackling a Batman Beyond movie should focus first on making a good standalone feature, not on setting up the future.
The fact that Warner Bros is released Joker, a 1980s-set origin story for the Clown Prince of Crime starring Joaquin Phoenix means that the studio is open to telling out-of-continuity DC stories.