I don't really believe this either. I'm not accusing you of lying, but are you sure your source is trustworthy? Because there's more than just one thing wrong about that list:
a) Barry, seriously? Barry has been featured in Mercenaries Reunion and Mercenaries 3D, both very recent games, so there's actually no reason to bring him back for RE6 Mercenaries as well, especially when you could have other more popular characters instead.
b) Who cares about Barry anyway? The fans are much more eager to play as Claire or Jill, and I'm sure the guys at Capcom know. Even Hunnigan would make more sense.
c) It has been confirmed several times that Albert Wesker is dead and will never return. Putting him in RE6 Mercenaries would only raise the false hope in some fans that he might return. Unless the Capcom guys have changed their mind about this.
d) And last but not least: No Piers?? Impossible. He's playable in story mode, so he has to be in Mercenaries. It's like a natrual law.