This was already the case for boats with ECDIS that complied with International Maritime Organization regulations.
Sort of...
The IMO regulations adopted in 2011 specified that paper charts were no longer needed as a backup if there was a second, independent ECDIS system on the ship. Those regulations for international travel still exist.
The Coast Guard is going a much further step to drive the last nails into the paper chart coffin - they specify the ridiculous nature of keeping paper charts up to date and no longer require them at all.
There was a time when I only used paper charts. You could easily tell because they were filled with pencil marks. I didn't update my charts because I wanted the latest ones; I updated them because they were so filled with pencil marks and erasures that I couldn't see much of them any longer. That's why we all updated our charts.
Today most boaters, me included, couldn't quickly do a DR plot on the most perfect, sunny, clear day, let alone during the rip roaring storm where you'd likely have to be doing it. I'm realistic about it. I have a degree in mathematics and used to do most of the DR calculations in my head. I couldn't think of doing that today - it's a skill that you have to maintain. Precious few people still have that skill because we all follow the moving blip on the screen.
I always love when others argue that they wouldn't move without their paper charts. Again, I was there and agree with how it used to be. But if you're going to say that now, then post a picture of your charts showing that they're up-to-date and filled with pencil marks. Because if they're nice and pristine, you're not using paper charts at all. You're maintaining a false sense of security since you couldn't really use them if you needed to. It's much safer to just keep a backup electronic nav systems somehow, even on a phone.