Sounds like it was lose-lose for Warner Bros. Either launch the complete game late or launch incomplete at the same time as the other versions.
On the bright side, at least the content is coming eventually. I'm not a huge fighting game fan, but if Supergirl shows up playable in the future and she's anywhere near as awesome as she is the DC Animated Universe (voiced by Nicholle Tom, plz), they can just take my money.