So these new activities will be available to players without the expansion right? they just won't have the bonus of closing the rift for extra rewards?

Rifts like in RIFT ?

This sounds a lot like the awakened invasions, except a bit more fleshed out? With probably a bounty-like boss at the end. I hope it's interesting (and challenging) if they plan to make this a cornerstone of the new legendary armour and the expansion.