I'm not even convinced that Bitcoin will be the survivor in the crypto coin wars. Most initial iterations of software are not the final useful form that becomes popular.
But bitcoin isn't software, it's a protocol. Open and upgradeable at that.
Bitcoin is both a protocol and a software program. "Upgradeable" means breaking the consensus and a new consensus must be achieved.
Easy to do, and was done at least once already. Just have the code be released as dormant in the new versions of bitcoin, have it track how many nodes have updraged, and then switch on automatically once about 90% to 95% of the network has installed the version with the new code. Users won't even notice the switchover as it goes from an old style block to a new style block. P2Pool publishes upgrades to their systems this way all the time, and unless you know what is going on, you wouldn't even notice the hard forks, other than installing a new version once in a while.
You are missing the point. When you tell new users that Bitcoin is easily upgraded the first thing say is that it must be easy to change the 21 million limit. Then Bitcoiners often respond respond with explaining the consensus and how hard it would be to change. This confuses people because if Bitcoin is so easy to change then many of the claimed benefits would be worthless.