I could NEVER say boring to Poison Ivy!!! Of course either Catwoman or Cheetah or BOTH will make the roster. Circe and Queen Bee are about the only other 2 villainesses that would even make since to add to the game. Black Canary, Zatanna, Power Girl, and Hawkgirl (if no Hawkman; no need for both) are also about it for the sensible females to pick from, that's not a lot of female characters at all. Oh and Star Sapphire or Killer Frost but I doubt we'll see those 2 compared to the other's popularity.
I do think that Killer Croc/Poison Ivy have a better chance than any other Bat-character because how MKvsDCU didn't have room for them and were asked for; same for Lobo, Doomsday, and Black Canary, they were all highly requested characters!
Also, if Poison Ivy did make the cut and they utilize plants/trees for background interactions, then there's more a chance to see Swamp Thing as well, same with Aquaman being in and utilizing water background, Killer Croc could make great use of it easily as well, unlike Bane in this case, he's more than just a basic brute character.
Plus Poison Ivy's history with other characters could really become unique for this game: Zatanna, Swamp Thing, Harley Quinn, Black Canary, oh and she's fought some pretty wild fights and even almost took out Superman; that is if it wasn't for kryptonite.
Plus her outfit/costumes are just pure genius, and her attitude is epically amazing in itself; LOL I love how she says she's coming for the Joker next in Arkham Asylum and how she just physically beat the $h!t out of the Riddle in the comics!!!
Thanks, I kinda see Poison Ivy as being Injustice's Queen Sindel, yet Black Canary gains the scream ability which IMO is a great trade, given that Poison Ivy has a WAY better ability and I'd really like to see some unique plant interactions with other characters as well. This specific topic for some reason reminds me of Rogue from X-Men just grabbing a tree while flying, ripping it out of the ground with the roots still intact and using it as a baseball bat, I kinda EXPECT to see that in this game, and graphically would be awsome seeing Wonder Woman or Superman do that! I'd also like to see Zatanna or some magic wielder make a tree come to life and kinda resemble "The Living Forest". Yet, I also see Swamp Thing as being a totally different plant manipulator than Ivy, involving his brute size which apparently he can even alter, and utilize plants to teleport; for a background interaction with a huge tree, he could be that over-sized fruit that falls off the tree squashing the opponent.