Watch the live stream at the moment. Some of the new mechanics look amazing, and the engine has had a very nice spit-polish with new physics and ray tracing.
Apparently the whole game will walk hand-in-hand with Path of Exile 1 and all of content and leagues so far and all content going forward is available to both games, it's just that Path of Exile 2 has a new branching story arc set after the events of Path of Exile 1.
