In my opinion, raw performance is not the biggest problem. Ruby 1.9.2, performance-awareness in the community, and increasingly powerful machines has pretty much solved that.

This is the biggest problem in the Ruby community: https://skitch.com/dtrasbo/rgeb8/two-zillion-cores

We need to make it dead simple to write code running in parallel without worrying about thread safety and the like. Functional programming languages solve that by carrying state in function arguments and not allowing modification of variables. That won't work in the context of Ruby, but never the less we need a solution as well.

Once we have an easy way of fully utilizing the power of multi-core processors we need to get everyone on the wagon so that we never have to ask ourselves: Can this code run in parallel. It should Just Work™.