In 50-100 years the gap is going to be so massive. Someone born 50 years from now have almost zero chance to own 1 bitcoin while there will be people holding thousands.
Does that mean new generations will have the motive to start bitcoin over again and start spreading the same way Facebook did? Starting from college students and get mass adopted later on?
You know, the simple fact a coin is called Bitcoin doesn't make it worth a lot. See all the Bitcoin forks.
Also a newly made coin may or may not become valuable, see the altcoins, in huge numbers being disappointing for the investors.
And, as a bottom line, the fact a coin (like bitcoin) worth a lot doesn't mean the world/the people get rich. No. Only few of the investors.
This being said, creating a new bitcoin may not make sense, especially if it'll be just a clone. I'd expect people will work in Satoshis in 50-100 years to overcome the price rise, but not much else.
So creating a new coin can (only) make sense if it brings something really new and useful to the ecosystem. And that's not related to the price of the competitor coins. Also that can be done now too, no need to wait 50 years. Again, see the altcoins, some did bring new useful features and some of those are going pretty much OK.