Tim Sweeney predicted that we'd all have 20 core machines with 80 hardware threads by 2009. Not really what happened.
The whole point is that while Ruby is nice, it's just too slow. Someone is better off investing time learning a faster compiled/JIT language.
Too slow for what? Certainly not all classes of problems. Heavy mathematical work (every number in Ruby is an object! That's going to be much, much slower than a C primitive!), sure, but there are lots of folks using it quite happily to solve a wide range of problems.
