I'm afraid that a few years is not enough. It takes 10-15 years for crypto currency to become common thing when you are paying in a store for example. Most people older 50 will never be able to use crypto currency, it's too difficult to understand for.
Now the information is changing very quickly. 100 years ago, information changed every hundred years. And now it changes many times a day. Therefore, old people also get used to such a rapid exchange of information. They will get used to crypto too. 10-15 years is a lot. In the crypto world, everything has changed for 1 year: it was attended by several times more people than last year. With this trend, crypto will quickly cover the whole world.