If you're looking at long-term prospects, my understanding is that the idea that computers have "speed", which "matters", is actually temporary (should stop around 2040 if current trends continue). At that point you run into the thermodynamic limits of computation, where the question is how much energy you're willing to put into your computation to get it done.
However, I'm not sure that affects language design a great deal. It seems to me the goal of a language is to let you express algorithms in a concise and efficient manner, and I don't see that becoming unimportant any time soon.
Well, I think we're sort of agreeing with each other. You said that speed should be irrelevant, because language design was about describing algorithms concisely and efficiently; I said that we should try and think outside the box, by ignoring our sense of efficiency. If it didn't matter how the feature was implemented, what features could we come up with that could radically change how easy it is to code? Maybe there aren't any, but it is an interesting idea. That is not to say that I'm only interested in inefficient improvements ;)
Lisp is an awesome family of languages partly because they have the ability to create higher and higher levels of abstraction via macros. "Complete abstractions" they were called in Practical Common Lisp. Are there any other means that could create "complete abstractions"? Or easily allow higher level abstraction?