Coreutils may have started as a clone, but quickly became so much more. While the 'traditional' unix tools were pretty much frozen when it came to new features, GNU was experimenting and adding new features and trying to improve the UX (which not everybody approved of). There's a reason why the first thing many people would do on a new Unix install was to add GNU coreutils, and in fact many of the GNU features eventually made it back into the traditional tools.
So the real question is will uutils eventually reach a point where it is better/different enough that people will actively want to replace coreutils on their GNU systems, or will it remain 'just' a clone.
Coreutils may have started as a clone, but quickly became so much more. While the 'traditional' unix tools were pretty much frozen when it came to new features, GNU was experimenting and adding new features and trying to improve the UX (which not everybody approved of). There's a reason why the first thing many people would do on a new Unix install was to add GNU coreutils, and in fact many of the GNU features eventually made it back into the traditional tools.
So the real question is will uutils eventually reach a point where it is better/different enough that people will actively want to replace coreutils on their GNU systems, or will it remain 'just' a clone.