Now such ideas seem completely out of place (and time) as Bitcoin is not serving the world even in its present state. Sorry if this is not what you wanted to hear but it is better to see what is really going on, however unpleasant it might be. Other than that, what you suggest is what altcoins already do, effectively expanding Bitcoin's supply
There's no point in any of us guessing where it's going to end up. It's early days still and anything could happen. This current period is a phase that'll pass. There'll be many more users who'll find many more uses.
The most likely scenario for more units being needed is machine to machine lightning network type stuff. That might become a reality without it getting anywhere near replacing a fiat currency.