Inb4lastcharacterisDrManhattan.
So basically what NRS is saying here is "we'll give you Martian Manhunter for free if you agree to buy the other three characters."
It's the same thing they ended up doing for MK9's 360 players after their guest character fell through... I don't really care too much about MMH, but I really don't see why he wasn't in at launch.
This is also a good way of saying "hey, check out our DLC fastballs" if they're announcing a season pass before release. Which is cool. Getting these characters out faster will mean less of a splash in the metagame pretty early on. All of MK9's DLC characters were pretty good. Even if I don't end up playing them I doubt I'll feel ripped off by this.