There is one other way to change the amount of coins in circulation however, the dev(s) have a key that lets them print money. odds are good the dev(s) will make a shit ton of coins from this and not delete the key. unless someone somehow gets the key then you can't add new currency technologically.
How does that work? As far as I understand it, new bitcoins can be generated only by creating a new block, 50 BC at a time (for now). If the devs have some way to generate new bitcoins quickly, that would pretty much defeat the purpose of having P2P network with no central authority. Instead of trusting banks, we would have to trust the devs.