Persona 4 Arena Ultimax. That must be why Atlus is making you free to acquire during the fighter's launch week (after which the DLC will require payment) So... yup, there's nothing to worry about here whatsoever.
Now you're safe and secure in that knowledge, why not relax and watch an hour of Persona 4 Arena Ultimax in action? You'll find Atlus' recorded stream below the break, showcasing some of the follow-up's new combatants including Sho, Rise and Ken (of Persona 3 fame and not Street Fighter sadly.) Apart from new characters, Ultimax brings new story modes to the returning ones, along with alternate shadow characters that play differently,
Persona 4 Arena Ultimax is due to launch on Xbox 360 and PS3 this fall.