During Sony's E3 press conference this year, Square Enix announced Final Fantasy XV and Kingdom Hearts III, both of which are under the direction of Tetsuya Nomura. As such, gamers shouldn't expect to be getting both of them within any relative proximity to one another, as each will take plenty of time in their own right before they're released.
Speaking to IGN, Kingdom Hearts series producer Shinji Hashimoto explained that because Nomura is directing both projects, it may be quite a while before Kingdom Hearts III is ready for gamers' hands. "So at E3 this year we announced Kingdom Hearts III and Final Fantasy XV. Both have Tetsuya Nomura as their director, so we can’t create these two big games at the same time," he explained. "It’s a difficult job, as we want each game to be perfect in terms of quality."
When asked why Square decided to announce the project so early despite the long development time that lies ahead for KH3, Hashimoto added, "A lot of people have wondered for the last couple of years if Square Enix has actually been working on Kingdom Hearts III; that’s why we announced it at E3 this year. But please, we need you all to understand that there’s a lot to do."
It's going to be a long and arduous wait, but one that I'm sure will be well worth it.