For me, what would do it is a complete product that is not niche. A Chromecast competitor that supports the big platforms and content providers out of the box (Android/iOS, Spotify/Netflix, Alexa/Google/Siri) would be ideal. This already exists in the Chromecast, except it's not open. Ideally, it'd just be software on a Raspberry Pi or any hardware.
Interesting. That's very different to what WebThings provides today but that's something I'd like to see too and have toyed with building in the past.
Chromecast was once very close to being an open platform by implementing the DIAL protocol (although DIAL also had some centralisation issues), but is now a proprietary platform built on the Google Cast protocol, and is creeping towards morphing back into Android TV.
There was once a project to build a Firefox OS based TV stick called Matchstick which could have been great (B2G is still used on current Panasonic smart TVs believe it or not), which unfortunately got embroiled in a debate regarding DRM and never made it to market.
The digital signage platform I'm currently building at Krellian (https://krellian.com) could be adapted to consumer use cases like Chromecast and I'd be interested in building that in a standards-based way (e.g. using the W3C Second Screen Protocol), but the challenge would always be getting support from the big content providers, and of course the issue of DRM.
