It would fragment user base between different languages, making it less united as community.
Which will complicate communication and help-ability of a community.
Additionally JS is more than enough for web games. Another languages are nearly not-possible in web browsers, and lead to many complications with cross-compiling, debugging, etc.
So we really can't see any benefits in another languages for PlayCanvas.
Currently it allows to script in JS, and use JSON, HTML, CSS, GLSL assets, which is far more than enough and covers all needs of html5 games requirements.