Square Enix has hinted multiple times that we should expect the "open world" to be the norm with mainline series going forward. Personally, I don't that it was necessary for Square Enix to say that, as open world is the logical replacement for the classic world map. World maps serve as symbols for the games world as a whole, but with where we are at with technology, there is no need to symbolize. We can Realize now.
Final Fantasy XV was SE's first attempt at a open world Final Fantasy, and you know what, I think they passed. At the same time I am sure that much more could be done, but I don't know what that much more is because I don't play enough open world games to know what XV is missing or could be better at.
What did XV do well? What did it not succeed at? What could future Final Fantasy titles learn/improve upon?