Nissan hasn't officially released how much cargo space the Ariya has, but from what I've been reading it should be slightly less than the Nissan Rogue, which has 39.3 cu. ft of space with the rear seats up and 70.0 cu. ft. with the rear seats folded.
Here's what Car and Driver
had to say about cargo space:
For all the information that Nissan has held back in the announcement of the Ariya, it has given us the car's dimensions. It's four inches shorter in length and height in comparison with the Rogue, but is more than three inches wider. The Rogue performed admirably in our carry-on luggage test and held 22 carry-ons with the rear seats folded, but we anticipate the slightly shorter Ariya will offer less cargo space.