everything requires a process, of course we can't replace it completely or totally, maybe to be able to do that we at least have to go through 2 generations so that all can access crypto in the internet world. at least being an alternative means of payment is already a good achievement now
I don't know what you mean by not replace it totally. In my understanding replace means to remove something as a whole not partially. 
People already use Bitcoin as an alternative payment tool, but still allowed in some countries. Yes, it needs the process to spread Bitcoin as the payment alternative around the world. Maybe it will take more than 5 years again to see Bitcoin be used as a payment tool alternative in most countries in the world.