With Navi still being GCN it is probably wont be much of a challenger to current nvidia anyway.
Not sure this is relevant, even with the same architecture, improvement can be very big, and with all consoles being GCN, I think it might be a good idea to keep the same.
On a different note, this is the same like saying that all intel cpu suck as they still use 40 years old x86 architecture, while we all know there have been multiple improvements to the original architecture.
The same is true for GCN, there have been multiple improvements over the years.