We know they are/were trying to make it totally seamless in FFXV and IIRC they've kind of hinted that they've achieved that when they said that Noctis & Co would be taking a real-time boat trip from that coastal area to Altessia.My main points of interest are:
-How will they handle the transition from town/city to worldmap (we don't know how this will be in FFXV either)
-Style and scale of the worldmap, 1:1 like FFXV or large zones like in FFXII
-How will the full party be handled on screen?
I'm not too optimistic on this releasing Holiday 2017, unless FFXV is at a stage very soon where the development team can start transitioning over to VII in mass.
It'll be interesting to see what kind of solution they'll do with the world map/overworld/overall structure of the game world in FFVII though, and probably the inevitable backlash when there is no flyable airship in the game, not with these kinds of graphics.