I view yarn as collective leverage over npm's product roadmap. As long as the npm roadmap doesn't stray too far from what developers want, or ship those things

I view yarn as collective leverage over npm's product roadmap. As long as the npm roadmap doesn't stray too far from what developers want, or ship those things too slowly, there should be no need to use yarn. But for that to work, yarn needs to remain a credible alternative, so that it's actually possible to overcome the switching cost.