I agree, but I think it's at the point were they have too many of them to put in a game...and the priority of who gets in would be a mess as well.
Since most SK games up to this point have been handheld experiences, I dont think they will have a huge playable roster anytime soon...hopefully thats what that PS3/PS4 game is about because If these characters did appear in a game, I wouldn't want them to gimp their movesets or animations due to limited memory/software space. That would be the ultimate injustice imo, because Alot of these designs are indeed better than some that made it into Shinovi Versus.
A late reply, but Warriors titles have been coming to handhelds with huge rosters for years with none of the issues you're suggesting - even if they added every single New Wave character that we have now, I think it should still be within the realm of possibility if they were willing to put forth that effort.
In any case, as sad as it would be, I can't help but think they would only add the Hanzo and Hebijo New Wave girls in a future game. I'd personally hope for a more varied selection though - but more than that, I think giving existing schools more characters might be beneficial too, instead of having them all have five outside of the "main" two.