I dont remember seeing anyone else post about this. There is currently a post on the Ultimate Alliance forums from a guy that works at Toys-R-Us. He states that they received the empty filler boxes for the game and that on the back of the box for the Wii version it clearly states these three characters are Wii exclusives. He didnt have pictures, but said when he went back to work today he take a picture of the box as well as the boxes for PS3 and 360. Could be total bs, but figured it couldnt hurt to share.
They've been rumored for a while now: http://marvelmods.com/forum/index.php?topic=3451.0
Still, there's no physical evidence, so I won't call it fake or true just yet.
Don't care, I will get the game for PS2 and XBox 360 (I try both, to know what's the difference and all). Hoping for a Nova or Sentry exclusive on next-gen consoles :D