One thing to remember is that NVIDIA did their "big move" towards a true ground up DX11 architecture with Fermi and paid the price. If AMD does the same thing, then they will pay the same price and learn the same (very hard) lessons.

AMD has essentially been using the same basic architecture since the DX10 days and has gradually added modules for DX11 compatibility. So, the move to a ground up DX11 architecture may be a tough one.