Considering that Shun'Ei doesn't exactly seem to be as front-and-center as SNK might have hoped, I could see them including Rock to challenge / liven up his position. Shun'Ei didn't set the world on Fire with his Rock-Tributes, so maybe he'd get his chance to shine once he can compliment the full idea, rather than replace him.
I'd rather have Mary than Rock, but I refuse to be mad at anyone that takes a spot over someone I'd want instead, ha. Everyone's SOMEONE'S fav... congrats to whomever gets who they want!
If that's really Yamazaki, Luong doesn't invalidate him, either. Same with Nelson and Nessa. And it's not like old characters won't get new-to-this-game tricks. Nelson isn't much for MAX mode, Vanessa could excel in it, as an example.
I'm almost looking forward to the Seiyuu work as much as the characters themselves. Not many characters share voices in this game, so would those who share one (like Mary) get replaced with new talent?