I don't believe the Mac is doomed. I do believe Apple will narrow its focus. Right now the Mac is something aimed at both the casual user and the professional. I think that iOS will continue to evolve as the operating system for the casual user and eventually Apple will introduce 'Macs' (that are running iOS - with an ARM processor and touch screen support) that are meant to service the casual user. The x86 Mac lineup will be pruned to power/professional systems only that aren't really meant for the casual user.
I don't think anyone is blaming Intel for the lack of Mac updates. Intel, AMD, and Nvidia have released a wide range of new CPUs and GPUs that would be fantastic in the Mac. Apple is definitely very slow to update their models.
The move to ARM certainly not because of some 'dead end' with x86.