Agree, I initially voted for JSON because knowledge of it is so useful, same as Node. These aren't huge language tracks and could conceivably be done similarly to the Command Line and Deploy a Website courses.
What the fine people at Codecademy need to answer is do they want to be our #1 source for a skill set (improving and adding to existing courses) or do they want to be a good entry level for ALL languages (what would happen if they started to devote themselves to covering C++, C#, F#, Clojure, etc.)
I would prefer the former, that we learn some JS, HTML, and CSS. Then learn to use Git and CL. Then work towards writing server based web apps and so on. It would be AWESOME if there was a track for each new yearly-ES update. Beyond that, you almost expect to have to pay for 'advanced' type instruction.