This info comes hot from a recent interview with Final Fantasy Brand Director, Shinji Hashimoto, while he was at Japan Expo earlier this month. The new project of Hiroyuki Ito is not directly stated to be FFXVI, but judging by how much depth Hashimoto says Ito is putting into the gameplay systems, it's definitely a game for PS4/One and one that looks to surpass the battle system complexity of ADB and Gambits in FFXII.
Full quote and source:
RPG Site: I can see Nomura-san's crew need the room back for their next interview, so I'm going to wrap up by betraying my inner fan and ask a more specific talent question - Hiroyuki Ito, the creator of ATB, the director of FF9 - my favourite, which of course you produced - and FF12... Is he still at the company - and is he working on anything that we already know about?
Hashimoto: [laughs] You're a very unique journalist, asking about Ito-san! Yeah. He's still at Square Enix. He's been planning and doing some proposals for a new project at the moment, so... Really, he's the kind of guy that wants to challenge new things all the time, so, yeah. At the moment, he's doing... [laughs] He's putting some ideas together.
RPG Site: I'm very interested to see what he does next. For RPG gameplay systems I really do feel he's one of the best there is; one of your strongest assets.
Hashimoto: Like you say, he's very talented and very involved. He's very, very in-depth... he likes the depth of the gameplay systems side of things. He really loves to go really deep on mechanics and things, and that takes time. I'm very excited to see his ideas soon!
Recordemos que los rumores apuntan a ambientación del estilo FFIX y sistema de batalla de FFXII.