I don't think they'll abandon it completely. I think they don't want the series to become stale and so they try something new every now and then. They tried something different with XII and now they're doing something different with XV. That doesn't necessarily mean XVI or any future games won't use a Turn-Based combat system or variant thereof. As has been said, XIII used ATB. I wouldn't be surprised if they continue to alternate between ATB and other combat systems.

My own personal preference... I like turn-based games. It's how I started Final Fantasy, and it's what got me into the series. But I do appreciate the need or want to expand one's horizons and be innovative. That's why I have no issue with XII's MMO-style combat or XV's action system. Turn-based may have gotten me into Final Fantasy, but that doesn't mean I think the series should be restricted to it, or that I want the series to be restricted to it. I just want a good game with a fun world to muck around in, and I'm happy with that.