I'm having the impression that OSes don't really matter for the vast majority of applications anymore; the main advantage of Linux is its licence and development model, by which I mean that it's a commodity. We use high-level languages to abstract away from the OS, and if we want reliability we make distributed systems using technologies like Erlang-OTP or Scala-Akka.

The only niche where I see an OS being relevant is in single-computer safety-critical applications and consumer devices. Minix3 aims for the former and I really hope it carves out its own little niche, but I think Linux is here to stay.