According to a report from
Geeks World Wide , new animated Batman Beyond film is in development at WB Animation and it's targeting a 2022 theatrical release. What makes this rumor slightly credible is the concept art that accompanies it. As you can see below, that's definitely a new take on Terry McGinnis.
Furthermore, Will Friedle's seemingly innocent Tweet about new Batman Beyond content only needing 'more time' is now looking a little more credulous. We'll definitely keep our ears to the street and follow up with any further developments. Just based on the interest alone, it almost would be foolish for WB to NOT have something Batman Beyond-related in the works.