We already have. God is not real.
It's often hard to prove something but it's close to impossible to disprove anything. How can you say, beyond any doubt, that God isn't real and there's no possibility of one? You can believe there's no God, sure, but you can never truly know.
To answer the question we can only really know after death (or if God decided to appear for some reason before that). Beyond that it's just faith.
I don't think even Richard Dawkins, back when he was relevant as something other than a Weird Twitter stalwart, claimed that God's nonexistence had been conclusively demonstrated, only that there was (in his view) no rational or morally acceptable reason to believe in it. This is a question that doesn't admit of proof one way or another except in the most speculative sense of "proof". Claiming otherwise is dogmatism.
