How about Perl, Ruby and C?

pg said that for a language to become popular, it has to be the scripting language of something popular. That's the category where the three languages I mentioned are falling.

So the answer is simple: one has to build something really nice in Nimrod and use Nimrod as the extension language of that thing. Maybe the embedded world would be a nice field from Nimrod due to having nice interop with C? (I haven't used Nimrod in my life yet, although I am tempted because it looks very easy).