AI coding assistants are closing the door. They need a lot of training data to be good and useful. Established programming languages have a tremendous amount of that, so AI coding agents will do a good job there. C, PHP, Python, Java, etc.
Garden variety and new programming languages have much less examples in the wild, so AI assistants will do a lesser job with those, unless their lineage leads to one of the established languages.
Finally, the bulk of future developers will be lured to AI assisted coding and therefore won’t generate much training data for new programming languages.
A vicious circle.
All of the above is speculation on my part, obviously. Maybe AI assistants will get smart enough to master languages they have not been trained on.