Yeah, I'm not so sure. Certainly there are many cases where a language was used for a type of project when it isn't ideal -- but it was the best option. A new language can come along and replace the old for that sort of project. But I don't really see that as "competing" in any meaningful sense. It's just that someone invented a better kind of screwdriver for that kind of screw.

Some languages can certainly become obsolete (although even then, I'm hard pressed to think of a language that is no longer used at all) or relegated to very niche uses, of course.