As in modifying the code on an agreement with all parties involved, is there a chance people might want more than 21 million Bitcoins?
Pretty good chance it will happen if bitcoin survives long enough into the future. Given the right leaders and the right circumstances the masses can be manipulated to support anything you can possibly think off. They got manipulated to support hitler. They got manipulated to support a war in Iraq and Afghanistan. Anything is possible.
If that happens I would be really upset and alot of others too will be upset. I dont think the ones that have the most bitcoins would want that to happen surely it wont be allowed to happen. Hence reason why Litecoin and others are here.