I can see a Batman Beyond movie happening only in two cases: 1) WB cancels the DCEU and chooses to make standalone films, but doesn't want to make another Bruce Wayne movie, so they go with Batman Beyond which maintains the Batman vibe while being a new concept, 2) the DCEU continues, but Affleck is too old to be Batman anymore after 8-10 years, so Terry comes in DCEU as the new Batman but isn't that "Beyond". Some will say that the second option is not the true Batman Beyond and they are right, but I don't think the general audience will care.