No, not unlikely at all. In fact, totally the case
I cannot prove that God exists. But I cannot prove the God does not exist (and even that would be contingent if you were positivist, because the conclusive evidence for either case could arrive at any point in the future). The hypothesis is not one amenable to falsification. That's the agnostic part.
But, on the availability of the current evidence, I see no reason to accept that God exists: there is no convincing argument to me that supports it. That's the atheist part: I do not think there is a God (or Gods).