I don't see anything in it that bodes badly for Stack in terms of traffic or financially either. I never said otherwise. They're dominant and given their answer base and the value of the content, they're likely to remain so.
I believe overall stagnation in the community is guaranteed however, which is what the topic rather focuses on.
Maybe we just aren't talking about the same thing. What does "stagnation in the community" mean to you?
If it means "overall, people lose interest and stop visiting to ask and answer questions," I don't see that. I'm not visiting to fill in all the gaps in SO's content, and feeling disappointed when there aren't many gaps to fill. I'm running into questions, Googling, and hoping to find my question already answered.
If I find it and it's not answered, I'll do research and try to answer it myself. If it doesn't exist, I'll ask. If I find the answer before anyone else does, I may answer it myself.
I'm not going to stop doing that, and I don't see why anyone else will, either. What the overall trends are in the site really has no bearing on my individual participation, so it never feels "stagnant" to me.
Maybe you're imagining users who show up and surf for questions to answer, and those people are getting bored? That's just not the way I use the site, though.
I believe overall stagnation in the community is guaranteed however, which is what the topic rather focuses on.