Actually, I believe the whole 'escape from Insomnia' part has been excised. It was part of the Versus XIII story, and was in the E3 2013 footage was was since confirmed to be a prototype build, but the story has apparently since changed, with the invasion now happening while Noctis and the guys are on their trip, so Noctis is forced to hear about his home being taken while not being able to do anything about it. I might be wrong but I'm sure I read about this in interviews.
Of course we'll almost certainly go to Insomnia - it's even on the map they revealed - but it might be later in the game.