What are you talking about? Pokemon X and Y? and the fan-predicted Z?
Possibly, but it's unlikely.
Not to mention, B for Black? Black/White/Black2/White2?
We're not sure yet, it's a little to early to be asking questions like this. It's all up to Gamefreak.
For future reference, try and be as specific as possible when asking questions and answering them. It's kinda difficult to understand what you're asking.
But if I understand it correctly,
I would not bet that Nintendo will make a Pokemon A and B. It doesn't follow the pattern that Gamefreak has laid out. It's too early to tell what they'll do, we haven't even gotten the evolutions for the starters yet. Just wait and see.