All the feature from distill should be now in Quarto. Main difference is that distill is based on https://distill.pub/ as mentioned by @radovan and Quarto default them is on Bootstrap. So features from distill have been re implemented, and improved (like listings with custom listing)
So I would say that as long as you are happy with distill, there is no reason to switch - it won't go away. If you want to try Quarto, then you'll find the same features and more. If you don't need R for your website (no R content in document), then Quarto does not need R contrary to distill who needs R to run.
So keep developing your website using distill as long as you are happy with it.