And a few years later, Intel said we'd get AVX512 on everything by 2016, and that the instruction encoding supported a future extension to 1024.

And then the Skylake and Cannon Lake debacle..

First they pulled it from the consumer chips a fairly short time before launch. Then the server chips it was present in would downclock aggressively when you did use it, so you could get at best maybe 40% more performance, certainly far from the 2x+ it promised.

Ten years on and the AMD 9950X does a pretty good job with it, however.