At risk of spoiling it for you, or others its best not to look into it. Its really bad. I'll just flag this down as a a big meh and avoid at all costs, should it come into fruition. Unless its directed by someone noteworthy and is not going to crap on source material. If you are interested, this is the article.
Eeesh, that does indeed sound terrible. Though other articles I read about the rumor made no mention of that replacement, in fact one of them specifically said that WB was currently doing scouting for an actor for Terry. So I will choose to remain hopeful for the time being. But if WB really is stupid enough to do Batman Beyond without Terry, they 100% deserve their reputation for making terrible DC movies and never learning from their mistakes on DC movies.