With a limited supply and growing adoption that we've seen that will continue well into the next decades, bitcoin is bound to be more valuable in the long run. It's simple economics, supply of bitcoin isn't going to get much bigger since it is emitted in a limited manner, while the demand of coins will go up over time as more merchants accept it for payments.
I do agree with this mostly, but we can't completely bank on a potential scenario where people are using their coins as currency, especially with how the volatile nature of this market won't just miraculously disappear.
What we can bank on is that Bitcoin will become a digital form of gold, and where gold doesn't need any use as actual currency, so will Bitcoin not need to be used as such, especially with fiat improving too.
In other words, the currency aspect will become a bonus on top of the store and cross-country-transfer of value utility. Gold can't do that conveniently, Bitcoin can and this will account for most of Bitcoin's demand.