The L1 button helps make Kratos the worst character in the game, if you use it, y'know.
Absolutely not, if 1 character will be banned it will be Sackboy.
Playstation All-Stars Battle Royale Accomplishments:
1st Ever rank 999 (only for full game, not beta)
1st Ever Double Black Belt In 1st 2 seasons (2v2 and Free For All)
1st Ever Black Belt (Acquired in Free For All)
1st Ever 2v2 Player to 300, 400, 500-1300 wins
1st Ever 2v2 Player to Black Belt level 300
1st Ever Free For All Player to Black Belt level 100
2nd Ever 2v2 Black Belt
Kratos is fine. Maybe reduce the knockback on his Forward+Square and bring down his AP gain by a little bit. Other than that he is beatable by characters like Raiden, Dante, Sackboy, etc. So no, I don't see Kratos being banned.
And a major reason Metaknight was banned was because his sword attacks (his entire moveset except one attack) had trancendant priority. What this meant was that no matter how much stronger another characters attack and no matter how long they charged it (if it allowed), the attack could never clash with Metaknight's sword. The nature of trancendant priority would result in Metaknight's attacks always emerging the victor. This along with his insane attack speed, small size, recovery options, and the fact that his inpenetrable sword covers his body, made him a character in his own tier on top with no troublesome match ups.
Kratos is not like this. He's good but he's not unfairly good, he can be beaten and a lot of the characters in the roster can put up a fight. Kratos is good in almost any match up but he does have some where he has trouble. And some stages where he's only ok.
Kratos is fine, he won't be banned.