On the contrary, I think that we haven't exploiting sequential machines to their full potential, and what's "holding us back" is all this theoreticism and overabstraction. There likely is a point where concurrency is really necessary, but one only has to look at the demoscene, full of people who have never formally studied CS, to see something closer to what hardware can really do -- and then wonder how so many others working in software, with formal backgrounds and extensive education in CS, couldn't.
This crosses my mind every time I hear about the MHz free lunch.
https://www.youtube.com/watch?v=oBegD7k2wvo , 02:20. JS and WebGL, which seem to be all the rage nowadays, would smoke the shit out of my i7 doing that. In case younger chaps are watching, the C64 has a 1 MHz CPU and a whopping 64 KB of RAM. For comparison, minified jQuery 2.0.0 is about 80 KB.
The JS/WebGL demos actually run on all of my machines, though.
Albeit barely :-).