I agree with everyone that this was an excellent piece. It did a great job of consolidating history in a short summary while never losing sight of its theme (and the game's theme for the planes): letting players and DMs make use of the Elemental Planes as a fun resource in their games beyond just a background device (and tracking the various sources, by name, wherein the game's different writers have explored this across the editions).
The Elemental Planes are one of the ideas where I think 5e has actually done a really good job of taking something that 4e did great work at making something really interesting and cool and working that into the more classic "AD&D" style (here the cosmology) that was used up through 3.5. The restyling of the Inner Planes and the Elemental Chaos in 5e is actually my favorite version yet of the elemental planes and one that I think works as the baseline for all sorts of really cool stories (especially because of how the differences in environments make for a more interesting matter than a static environment, especially if the PCs are up against foes for whom moving deeper into the planes isn't the same sort of trouble as it is for denizens of the Prime Material Plane).
Given the amount of resources out there via digitized adventures and sourcebooks, as well as how easy it is really to effectively convert things to 5e, these sorts of articles are great. I can easily imagine some readers chasing down some of the mentioned items here on DriveThru or something and converting adventures or taking background info for use in an elemental campaign built around Elemental Evil – exactly the sort of thing that WotC should be doing to quietly market forty years' worth of back catalog!
