Hey, I was also at Demuxed last year! I help maintain Hls.js; it should have some form of LHLS support by soon(tm). There's no standard yet so actual adoption will be tough (current implementations use non-standard EXT-X tags to signal LHLS). But pretty much everyone does the same thing: early signaling of segments, chunked transfers, and on the client side, progressive demuxing. HTTP-based solutions typically achieve the aforementioned 3 seconds, but anyone talking about LHLS now (Akamai and Wowza) have their own protocols; it remains to be seen what the rest of us will get.

Twitch has recently implemented LHLS (looks like a "periscope-style" implementation) and I was seeing 1.2s glass-to-glass.