Probably way, way over the line. Population sizes exploded after the agricultural revolution. I wouldn't be surprised if the maximum is like 0.1-1% of the current population. If we're talking about strictly eating what's available without any cultivation at all, nature is really inefficient at providing for us.
Do you mean for everyone to be hunter-gatherers? Yes, that would be impossible. If you mean for a smaller number then it depends on the number.