Bitcoin has unique properties that no other asset has, I believe that these properties are the real value of bitcoin. Bitcoin does not need to be backed by anything except its properties. I believe that the main bitcoin purpose is a store of value. Many people say that bitcoin is not used as a medium of exchange and that's true, it's not convenient to use it because transactions are slow and fees are high for small purchases. People don't use bitcoin to buy stuff, people use fiat because it's more convenient, right? We have so many really good mediums of exchange, does bitcoin need to be one of them and compete with them? Hell no.
Let's look at bitcoin from a store of value perspective. How would a new store of value adoption look like? What is the measure of it?
Just two things:
1. Accessibility, convenience of buying and selling bitcoin.
2. Level of people's trust (most important)
More people believe that bitcoin has value, more valuable it becomes; that's a simple rule of a store of value. So, bitcoin adoption is in level of people's trust. The higher level of trust bitcoin has, more adopted it is. I think while bitcoin keeps its properties, it will earn people's trust and become more and more valuable. In 20 years, no one will ever doubt that it has value and the exchange rate will reflect it.
When we are talking about how useful it is for buying/selling stuffs , we have to first think if the network is equipped enough to handle these kinds of transactions , we are not at that level right now that we will be able to use lightning network without being scared for the funds since it's not that safe.
In the meanwhile we will see some upgradations in the future too , the network will improve and we might have a system where we might be using Bitcoins in day to day activities .
But right now the main focus is Investment. Which depends upon the stability of Bitcoins and what it can offer that other cryptocurrencies cannot.
We have a cutthroat competition out in the market like ETH there it might be technically superior but at the same time Bitcoins is old and trusted by millions , it started the whole thing and it's not much about the competition as it's about the symbiotic relationship the coins have in the market , one coin very easily escalates the price of other because of the trading pairs.