I don't think most developers have the capability to be sysadmins or QA. Vice versa, too, quite often. Joe developer ain't that special.
Devops is about taking moving the infrastructure into its own configuration-managed artifact, taking lessons from programming and computer science, and coming out with its own engineering rigor.
If you want your devs to operate builds/infrastructure/etc/etc, that's fine, but devops that ain't. That's called "many hats".
- systems is about thinking how different things fit together
- development is about building something
- quality assurance is about figuring out how to blow something something up
The thing is, I know technical people that I wouldn't trust to do one of the above, let alone all three at once. And I know people who can rock it in multiple disciplines. When it all comes down to it, focusing on the quality of the people you work with and helping them thrive is a solid plan.
No, but they tend to think they can.