IMO, there's rarely such a thing as maintenance mode. Projects constantly evolve, and in turn this drives more investment in tooling and the ecosystem needed to keep those projects up. And this investment is what eventually drives more new projects and fresh blood, keeping the language fresh and in demand.

Again, look at Java.

Ofc, there's always the question of what happens with a market that isn't constantly growing due to zero-interest rates phenomenon. I guess we'll see, but IMO, that's problematic for newer languages, not established ones.

I too am a contributor of very popular libraries and am very familiar with ecosystem. One thing to keep in mind is that the language's culture has evolved. When I picked up Scala, back in 2010, the Future pattern and Future-driven libraries were all the rage. Whereas nowadays people prefer alternatives which now includes blocking I/O (Loom), with Future-driven libs being a risk going forward.