Presumably it'll go:
Noctis: "Is my dad really dead?"
Cor: "You want the truth?"
Noctis: "Why not?"
Cor: "It's complicated."
*Cor walks off and the issue remains a mystery until a shocking third act reveal*
Tinfoil Theory #92
The reason why the invasion at Insomnia gameplay has been cut is because Regis does not want Noctis to know what's going on. Tabata did say it's for story related reasons anyway.