I disagree strongly with the author,

Yea I designer can learn how to do dev stuff, is he going to do it efficiently in a work environment? I think not. The author talk about front-end development like it's coming increasingly easy, it's the contrary, it's more complex than it ever was.

Front-end development is not anymore about doing some css, html & creating a poorly written jquery plugins. It's a whole stack now, you got preprocessors to make css more powerful, a whole lot of tools to automate process, and js mvc to the booth & much more advanced javascript code to handle.

Is there exceptions? of course there are, some engineer are incredibly gifted designers and the other way is true, but in general? it's going to stay separate jobs.