They are already confirmed to be in the game, there's no point for asking again for them, lol
Anyway, i personally think that there will be like a two character limit per series, since it's a 2 vs 2 game, a character pair could work well for a possible story mode (like with Street Fighter x Tekken or Project X Zone), but yeah, just a guess.
The already confirmed Pairs
-Goku & Vegeta
-Naruto & Sasuke
-Toriko & Zebra
I guess the other characters could be:
-Zoro (paired with Luffy) (One Piece)
-Uryu or Rukia (paired with Ichigo) (Bleach)
-Killua (Paired with Gon) (Hunter X Hunter)
-Hiei or Kuwabara (paired with Yusuke) (Yu Yu Hakusho)
-Sanosuke Sagara (paired with Kenshin) (Rurouni Kenshin)
-Pegasus Seiya & Dragon Shiryu (Saint Seiya)
-Jotaro & Polnareff (Jojo's Bizarre Adventure)
-Bobobo & Don Patch (Bobobo-bo-bobo-bo)
-Yugi Moto & Seto Kaiba (Yu-Gi-Oh) (or instead of Kaiba, Yugi could be paired with Yaden Yuki maybe...)
-Train & Eve (Black Cat)
-Yoh Asakura (Shaman King)
-Allen Walker (D Gray Man)
-Tsuna (Katekyō Hitman Reborn!)
-Kenshiro (Fist of the Nort Star)
-Kinnikuman (Kinnikuman)
-Arale (Dr. Slump)
-Kid Goku (Dragon Ball) (Yeah, i resquested kid Goku because the Dragon Ball environment is much different than the DBZ one, and his moveset also differs greatly (Power Pole, Oozaru, etc...))
-------------------------------------------------------------
Maybe we could get Villains as well, they could be powerful enough for be a one-man pair, and be one for each franquise. If we have story mode, it could fit very well as game Final Bosses.
-Frieza or Kid Buu (Can't decide, Frieza has personallty as is more popular, but is weaker, and Buu is more powerful, but lacks personality)
-Tobi (4° Ninja war Costume)(Naruto)
-Ulquiorra or Aizen (Bleach)
-Younger Toguro (Yu Yu Hakusho)
-Shishio (Rurouni Kenshin)
-Hisoka (Hunter X Hunter)
I don't follow One Piece, so i don't know which villain is the most prominent/important that luffy faced up to date (maybe you can help me with this one, Steven
). Same goes with Toriko..