There is more than one threat that the traditional role of sysadmin is facing these days.
DevOps is gaining momentum. Not only is it expected that you can do all the operational stuff, but to be able to code as well. This is quite daunting to me since I support Java, .NET, Perl & Python applications. Sure, I can script, and can do basics like HTML/CSS/Java Script/JQuery but who the hell has the time to not only learn but be proficient at all that?!
My role is being automated away piece by piece. Apps like Chef and Puppet make spinning up new servers a breeze. I actually think having systems like this makes a lot of sense for the business, but not for my future... Take AWS for example, you can fairly easily spin up an elastic service that leverages OpsWorks for configuration management.
Speaking of AWS, as cool as it is, is a threat to a lot of sysadmins. Who needs a network admin when it's all done on the cloud? Or a Windows/Unix/DB admin? Services like AWS makes spinning up servers child's play, at a very competitive cost. Need a simple AD environment? Literally like 4 clicks away. Traditional infrastructure support roles are in the same tight spot.
Outsourcing... There are lots of companies that are willing to do my job. Take my wage, outsource it to India and keep the change. They are really good at selling themselves to upper management. The reality is that the support these places offer are much lower than what my team and I have been doing, but good luck convincing some VP of that. By the time we've been laid off and they realize that they have made a huge mistake it will be too late.
That's the end of my rant I guess. These days it seems to me if you want to maintain a sysadmin role you have to be 1 of two things. Be a part of a basic support staff like Desktop, because people are always going to need localized support for their dumb mistakes. Or be one admin to rule them all, rolling in development, sys admin, network admin, windows admin, unix admin, cloud admin & automation all into one package....