I've seen different translations of the interview I mentioned. Some say that the game won't be released as a complete edition later on, while others don't state that, so I don't know if Nomura really said that or it is just a mistranslation or different interpretation. This is what was posted on KHinsider:
Are there plans to release a Final Mix version of KH3, containing extra content?
Nomura: I’m not really considering it at the moment. Well even if I wanted to, it wouldn’t fit on disc (wry laugh). We’ve got plans to release game updates through DLC, so if we were to add content it would be through that, instead of in the “Final Mix†format.
We’re yet to fine tune the details, but we won’t be doing things like having Keyblades for sale, instead we are looking more at gameplay expansions. And not in the form of any sort of “Season Passâ€, we plan to deliver the content as is in individual packages. At any rate though, first priority lies in putting our utmost into delivering the best main package we can, and then we shall see about the rest.