What language/framework you thought was the future but ended up dying?

WPF. Thought it would be the future of development for Windows. I think it isn't dead yet, but there seem to be serious doubts about its future. Maybe UWP killed it.

From languages I would have thought that golang and rust would make larger inroads, but maybe that is still to come.

Honorable mention would be Java an in particular "agent"-frameworks. Thought it would be the future of automation. Perhaps people actually use it, I just haven't seen it implemented anywhere.

NaCL:https://developer.chrome.com/native-client/nacl-and-pnacl

If I might expand the question to be about technologies in general, I'll submit OpenSocial[1] and Widgets[2] as two things I thought would be widely adopted, but ultimately weren't.

[1]: https://en.wikipedia.org/wiki/OpenSocial

[2]: http://w3c.github.io/packaged-webapps/api/Overview.html

For a brief amount of time I thought Dart would eventually push through in the web. It was interesting to see it's resurgence in the domain of mobile recently though.

On the other hand I didn't exapct Go to go anywhere. I remember briefly paltong with it a few years before it became popular and kinda just set it aside because I thought it was just some random toy language from Google.

Enyo was an unfortunate victim of the failure of the TouchPad. The actual JavaScript framework was/is great and was actually the real precursor to React. Some of its core component based principles made it there. The original Enyo team breathed some life into it again by releasing Enact, a React based framework inspired by the original Enyo.

Old school Enyo is hard to work with these days and there are many many dead ends and the community is majorly lacking but for a sheer JavaScript framework it’s one of the originals and the best.

https://enyojs.com

Meteor seemed interesting but poor leadership doomed it to maintenance mode. I guess it’s apollo, Now? Unfortunately I think it had the same leadership. Pitty for the various brilliant people there who bought into the vision

A rich internet application (RIA) framework--any of Adobe AIR, Silverlight, JavaFX. But they competed and none gained enough traction to become dominant. This happens over and over with universal toolkits. The current one is html+js web app/electron. Not my fave in terms of developer ergonomics or resource efficiency.

polymer + haskell