Famitsu magazine has confirmed that Fuuka, main Persona 3 character, will appear in Persona 4 Arena as an announcer during battles and such. It says that she's now a university student, as well.
Given that it's Fuuka, she might have an important role in the story given that she's most likely a member of Mitsuru's "Shadow Hunters" organization. Hopefully her voice transformed as she got older.It had been speculated before this that she would be a member of the cast because of these two images:
Because of this, maybe the above image depicting the "Shadow Hunters" is more significant than not and might hint at other familiar characters that might appear in the game.