What you fail to realize is there is no "we".  You will never convince every single user to start calling a satoshi a "Bitcoin".  Names only have meaning if they are consistent.  Imagine if at the same time there was more than one definition for a meter, it would be kinda useless to provide units in meters (which definition of meters).  In centralized institutions the central body can proclaim a new change in value (like redefining a meter, or kilogram) but that doesn't work in a decentralized network.

Can you imagine would utterly confusing it would be if everyone you talked to had a different definition of what 1 BTC was?

A BTC is NEVER EVER going to change.  To do so would require a consensus, it would require rewriting everything that has been written.  It would still lead to confusion and chaos when people looked at outdated articles talking about (there will never be more than 21M BTC and the person own more than that himself).  It simply is not going to happen.

Most of the time you can't get 100 bitcoiners to agree on just about anything but somehow you are going to get millions of users to simultaneously change their definition of what a Bitcoin is?  Really?  That seems a viable solution to you?