@OP, you are talking about digital assets replacing cryptocurrency. Have you ever thought of or researched on what digital assets are. Cryptocurency is an example of digital asset, since it is something that has value, with online presence, but does not have physical presence. There are also other forms of digital assets, so you need to be specific on which you think will replace cryptocurrency.
In my own opinion, we are yet to see an end o cryptocurrency. It has a great future ahead of it.