https://en.bitcoin.it/wiki/Prohibited_changes
These changes require the consent of every bitcoin-holder:
Increasing the total number of issued bitcoins beyond 21 million. Precision may be increased, but proportions must be unchanged.
Deviation from this changes a fundamental property of Bitcoin so you essentially are created an Alt. While hypothetically possible that 100% of people would consent to this change it is extremely unlikely knowing what we understand about human nature(we are selfish and are not going to adopt a change that destroys our savings and framework we depend upon), and the fact that miners don't solely control the vote but users do on this change.
Prohibited changes? Decided by who? Some Bitcoin dictator? Bitcoin Central Authority?