RethinkDB was something that I though would still go strong without the backing. I never used it and was never involved, so I'd love to hear what happened when the company died.
(One exemption is Xfree86 though, which was forked successfully by to community to Xorg if I recall correctly)
A light IDE is not rocket science and this project is known (and loved) by many open source developers.
https://electronjs.org/apps?category=games
HTML5 and Canvas do work on Electron after all. :) I feel there was some post on HN about a game released under Electron to which the reaction was "I didn't know it was made with Electron!" not a month ago.
Edit:
Also Atom wasn't a testbed for Electron. Electron WAS MADE for Atom afaik. They only opened up Electron after Atom was out for a while, it'd be the other way around if what you're saying is the case. I think Microsoft is already heavily invested in Electron. If anything they will provide even more resources towards Electron itself.