I imagine they won't bother announcing it until we get closer to the VII Remake release. As it stands, nothing is going to really capture player's attentions until that "elephant in the room" is released. Even then, I imagine it will get a real announcement around the time Episode 2 is close to release and nothing short of a "yeah we're working on it" will be detailed until then.

What it's going to be like will be another story and will largely come down to who is directing it. I imagine it will be handed to Toriyama since his team isn't doing anything at the moment, and SE doesn't usually let the same director go twice in a row anymore, so people worried about XV's director working on it can breathe a sigh of relief. There is also the possibility they may tap a new person to work on the title, which I would prefer but that's a double-edged sword in itself. Sadly, I'm getting more and more pessimistic that any of the old guard (Ito, Kitase, Tokito, and Kawazu) will ever direct a main entry again. I feel SE is trying to move the creative side of things to a new generation.

Since the games have a bad tendency lately to whiplash back and forth from extremes in style, I imagine XVI will be a much more story driven and linear experience with a convoluted, but ultimately simplistic battle system tacked on in order to "win back the fans" who hated FFXV's open world Action-RPG shenanigans. That's assuming no new gaming trend doesn't take the world by storm in the intervening years that ends up capturing the style they want to go for.