Imagine a hypothetical situation where the people who will ever get born are 50 billions. If each one of them knows how many people were born before him, he could make a prediction on how many people will be born after him by doubling that number. This would be roughly accurate in the most cases, theoretically even in the case that the answer is "infinity" (if I'm not wrong here).

Therefore, since it's estimated that 100-115 billion people have lived so far (source: Wikipedia), would we expect about as much, if we ignore everything else we know?

I feel that there is a good chance that I'm wrong, but I've checked this hypothesis several times and I don't see any mistakes, except that I'm not sure about the case where infinite people will be born.