However, I think as with most things that involve computational thinking and automation, this is not a zero-sum game. A developer who can apply deterministic, testable processes to server-ops may be able to reap an adequate amount of benefit for significantly lower cost than a specialized sysadmin. In addition, the developer is augmenting his/her own skills in the process. Yes, that dev was not able to focus all of their time on...whatever part of the stack they are meant to specialize in...on the other hand, the time spent studying dev ops is not necessarily a sunk cost.
For my own part, I've tried to stay away from sys-admin as much as possible...but when I've been pushed into it, I've gotten something out of it beyond just getting the damn server up. For example, better familiarity with UNIX tools and the importance of "text-as-an-interface"...which does apply to high-level web development...nevermind the efficiency you gain by being able to stay in the shell when most appropriate (rather than, say, figure out how to wrangle server commands in a brittle capistrano script).
But hell, even the end product itself, just being able to deploy a server with some confidence...is kind of empowering. For me, it opens up new ways to run scripts and jobs...It sounds dumb and maybe it's just the way my brain poorly functions, but the concepts of server-oriented architecture become so much clearer when you can spin up different machines to play with and experiment with delegation.