Today bitcoin is already known worldwide. So we dont need 6 years to be able that all people will be using bitcoin. Were living with advance technology today, and were still uprading every year. It means that even next year bitcoin will be use by almost everyone.
Actually the moment bitcoin was released, it can be use by everyone worldwide but the case is, people does not know about bitcoin that time or people are hessitant to use it and not everyone has the capability to use it.
But we are discussing here about everyone (every people in every corner of the world) will use bitcoin and that is impossible to happen even in 10 years more. The fact that not everyone has connection to the internet. And not everyone is aware especially those in ethnic region. So there is no chance that Bitcoin will be used by almose everyone in 2022, you can say almost everyone in the internet but in the world it is a no.