It means there is nothing we cannot do, there are no limits.
150 years ago, we thought that flying was impossible – and here we are today, flying all over the earth in a matter of hours.
They said we could never get into space – you can check that off the list.
Move faster than sound – check.
Cure cancer – check (some manifestations ofcourse)
We can do anything with the accompaniment of time and effort as we have proved



Infinite potential until something happens to prove us wrong i.e; intergalactic catastrophe/space plague.
edit; when they say “humans” they say it in the plural.
One way of interpreting that could be that Humans as a SPECIES have infinite potential.
Infinite potential is the inveterate ability to achieve greatness in any and all of its forms.