So, wait. You can print your own money subject to a cap? ie. creating bitcoin only involves spending CPU cycles (or electricity)?
Any change would need 50% + 1 of the bitcoin network to follow the new rules.
An effort to change the software to "mint" a greater amount will be countered by those who already hold bitcoins, and can add mining capacity to resist the change.
Another implementation could be launched with a different limit, but that would be a completely separate, new currency.