I could easily see Minato Arisato/Protagonist /Makoto Yuki be a playable charcter. Maybe between Persona 4 Arena and 2 Elizabeth has found a way to kill Erebus for good and uses the help of the P3/P4 Cast in order to help her act out her plan
I wouldn't mind just 4 New Charcters i just would like to see 2 More and counting the Shadow Versions..that would bring the number of charcters to 34 which is a great number for a fighting game..if there are two more charcters left..i hope they are from Persona 2
If this is a Sequel than i would expect 4-6 New Charcters..ASW are probably working on this game as we speak..i think it's pretty responsible to expect more than 4 Charcters in Persona 4 Arena 2...
So..character predictions:
My guess is that we will around about 6 New Characters..
3 - From Persona 3: Koromaru,Yukari,Junpei Iori
2- From Persona 2: Maya Amano,Tatsuya Suou
1 - from Persona 4: Tohru Adachi
True..but you never know..i hope not all the charcters are from Persona 3..also i have a feeling that this is to build up hype for Persona 5 which is going to be revealed at TGS..