In the latest issue of Famitsu, Atlus has taken a two-page ad out that hints at an announcement on August 1st. According to a quick translation from the folks at NeoGAF, the tag reads:

On the day when Yin and Yang come together a new jiken (event/incident) will begin.

Seems like this is another Raidou Kuzunoha game. Any other guesses?

Atlus mysterious ad in the latest Famitsu... [NeoGAF via Go Nintendo]