Shiki isn't a surprise given her brand new shiny sprite, and seeing as we got Genjuro, I'm willing to bet that Mars People will turn up as a rival to Marco, and possibly Earthquake as well.
Mudman... meh. I'd rather see Janne, the only interesting character from that game. They could probably figure out some really cool stuff with her whip-sword. Though, with three World Heroes and one from Aggressors of Dark Kombat now, I don't think there will be any more.
Still want to see Galaxy Fight and Matrimelee characters. SNK owns Noise Factory now, so just put those guys in there! WITH their music.