It's not sustainable because Intel will fight back. The only question is how soon.
AMD has all in the performance metrics but only up to 20% market share in the x86-64 desktop segment, while only 5% in servers.
They could have had all if they offered a 16-core for $400 - literally 100% of the sales but obviously they don't want to.
I'm sure you know better than the entirety of AMD's engineering, marketing and sales departments. If only they could act on this amazing wisdom you have for them?!
With regards to servers, not all companies go out and buy new server hardware every year so growing the share will naturally take time. Also if other businesses are anything like the one i work for it takes a while to convince the key people that they should move away from Intel when they've been on Intel forever. No IT department wants to be responsible for breaking apps and things by moving them to new processors/hardware unless they are sure it will be seamless. Of course cost comes into it and cheaper is always a good bargaining chip but architecture moves are rarely straight forward.