But we should also consider that BTC is still the best implementation of a cryptocurrency. And if there was something that's gonna outlive every coin in the space, it's still gonna be BTC imho.
The rest haven't really been tested at the same scale that BTC has.
The lasting legacy of Bitcoin will be the total market cap of the cryptosphere, this pool of wealth is only 10 years old, and unlike any other in human history, it is free of conventional control, growing over time, and can morph itself into other forms almost immediately with minimal costs. Bitcoin and all other current crypto tokens might not exist in 10 years, but the pool of wealth will, it will continue morphing into new tokens by new tech as long as humans exist.
I liked your post, this is what I thought of after...