The protocol is used all over the place (Telecoms, NATO, Games, chat apps, IoT, chat ops) and I expect that to continue.
We might never see mass adoption of the idealistic kind.
That said, having a healthy XMPP ecosystem is still important even without mass adoption.
It provides an escape mechanism out of oppressive surveillance and I believe if circumstances were right (i.e. things get bad enough) it could gain mass adoption and be an important tool for exercising freedom.