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.