The only limitation to potential is that which we impose on ourselves. There are many examples of people surpassing all expectations throughout history.
So you really believe that there are no inborn differences between humans at all?
Nice idea, but unfortunately the evidence indicates somewhere between 1/2 and 3/4 of human intelligence is determined before birth. It can be degraded but not increased, as with so many human characteristics.
That some people exceed their own and others expectations does not address this issue at all. It just means that the expectations were mistaken.