XMPP is a lot like email. There is no money in it and it has warts simply due to the fact that it is a widely implemented standard. You use it mostly because it is a well developed standard with lots of support. I don't know what it would mean for it to become "popular". How would you tell? All you can know is what your friends are using. An IM protocol is a silo...
There is a lot of interesting XMPP stuff happening right now with respect to the currently hot topic of privacy which could affect XMPP popularity.
There are over a hundred known public XMPP servers last I looked. Due to Let's Encrypt those servers are now encrypting the server to server and client to server links in a meaningful way.
The encryption from Signal has been integrated into XMPP with OMEMO. This suddenly makes XMPP a lot more interesting in terms of privacy. The clients are mostly moving to OMEMO end to end encryption which as a nice bonus eliminates the user awkwardness with the last thing (OTR):
End to end encryption is basically impossible to do properly with a web client. An interesting discussion for Movim can be found here: