I heard during FFXIII's development, once they made the vertical slice for the demo included in some bluray, their vision became unified and development went so well that they didn't miss a single deadline.In the case of Kingdom Hearts III, since they are using UE4, I don't expect any technical issues to waste development time. I think Nomura also said that the game's worlds have been developed but now they are filling them in with details and polishing. I don't think there will be any delays.