Will the combat-class changes go live pre-expansion?

[Knahli]

The preorder grants you few days of pre-access to the game where everyone can try the new things.

Let's be honest though, as far as anyone waiting on the expansion is concerned, Early Access IS the official release date. Unless those four days were specifically unfavourable for you or you had only a fleeting interest in FFXIV, then there's literally no reason not to pre-order as far as I know?