First, the source:
http://www.bemanistyle.com/index.php?news_id=418 (thanks to cj iwakura for the information).
Known stuff so far:
-It'll feature not only the Zero tracks, but also some songs from NX itself (including Chimera, You inside my dim memory, FAE2-1, FAE2-2, etc).
-It'll have other unlockables, like Zero's noteskins.
-The unlock system will be replaced (YAY!) with some kind of store, where you can buy the songs and all the hidden stuff.
-Story Mode?!
-It has Easy Station, like the original Zero.
-Adhoc modes for 2 players.
*Goes quickly and preorders*