From the Gamestar preview thread ar TWC

Apparantly we will get three kind of governments: Absolute Monarch, Constitutional monarch or Republic.

The diplomacy AI will be improved Alot according to them. And other monarch factions will dislike the fact if your empire/kingdom becomes a republic.

The taxes will be paid in a new way.
From nobility, citizens and peasants. They will pay their taxes separately.

Also, it seems like we will get north africa, south and north america, and the indies.