Atlus' parent company, Index Holdings, has dissolved the the company as an independent company according to their official announcement on Index Holdings website.
Index Holding acquired Atlus in November 2006 in a stock buyout. It is also the owner of game company Interchannel and animation studio Madhouse. It's current goal is to streamline its focus to "profitable core areas."
Katsura Hashino, director of the upcoming action horror title Catherine mentioned the shift in the company on the official dev blog, saying that the team "will endeavour to continue to work for a long time" and "of course, it's not just the Persona team, it's also other teams working on titles."
The Atlus brand will still continue and current projects are unlikely to be cancelled.