Both are correct, but mean different things. "Who will you be?" is asking "who you will turn into, what kind of person will you turn into?" "Who will be you?" however, is more likely a question that is asked when someone is filming a movie about your life, and asks, "who do you want to play you (as a role) in this movie?"

The correct way is: Who will you be? The structure in the simple future is: Subject + will + verb + complemento. (Affirmative) Subject + will not (or won't) + verb + complemento (Negative) Will + subject + verb + complemento + ? (Interrogative) I hope this help you, saludos!

Ciao Paolyta I hope that the second question is correct because in the interrogative phrases the verb goes before of the pronome. I wait with you another comments Gaetano

Thank you so much Joe!!! :O)

Either one all by itself without context doesn't really make much sense. The first one can work in some situations though example "Let's play Monopoly! Who will you be? The shoe or the dog?"