Phantasy Star Nova is a single-player/co-op RPG coming to PS Vita next year, Sega announced at Sony Computer Entertainment Japan's press conference today (via Gematsu). The tri-Ace developed title has not been confirmed for release outside of Japan.
Nova takes place in the same world as Phantasy Star Online 2 (which has been delayed indefinitely outside of Japan), but emphasizes the single-player story over huge multiplayer hubs and missions. Giant monsters like the appropriately named Gigantus and four-player co-op also indicate the long-running JRPG series may be taking some cues from Monster Hunter.
Judging by the Phantasy Star series' recent history, the chances are not-good-to-pretty-bad that Nova will ever see release outside of Japan. Either way, we'll learn more about it at the Tokyo Game Show next week.