This is Apple's Achilles heel.
If another company could release something like the Duo that seamlessly switches between phone, tablet, and desktop experience and make it Apple quality then Apple are in trouble. The technology is all there since the days of Ubuntu Touch.
Sadly I don't think there is a company in a position to build such a device that could compete.
I don’t think Apple will ever do it.
I personally would like to see the phones behave like iPads when connected to screens and mice and such. I don’t need it to pretend to be a full Mac.
But we all know they’re on the same OS at this point. iOS and iPadOS are completely identical, and this only makes it more obvious.