Atheist is someone who by definition lacks belief in God.
So atheist can never believe in God. Person who believes in God is theist, not atheist.
My opponent defends a position that at some point in future, an atheist will believe in God. But that is logically impossible. A theist will believe in God. Atheist wont, ever.
Lets break up topic by definitions:
A person who lacks belief in God will never believe in God.
the moment person starts believing in God, person is no longer a person who lacks belief in God.