DJ being banned is mostly a logistics issue. It's been said several times that once there's a pre-made, instantly selectable Devil Jin available, he will (probably) be allowed in tournaments. I don't know why people keep missing this. If you don't agree with that, take it up with tournament organizers, because they can argue their position better than I ever could.
Besides, if he were to be allowed now and banned later for whatever reason, there would probably be a lot of bitter DJ players to deal with, because they'll have spent weeks or perhaps even months learning how to use him.
Bottom line: If Project Soul is convinced that DJ is meant for competitive play, they should do the right thing and put the damn character in the game. Until they do that, he's banned.