So somewhat similar to Java ME 8 Embedded, targetting IoT devices rather than phones, Mozillla also hopes to escape an overly dominant Android (and shrinking, but still very popular iOS) on phones: http://www.theverge.com/2016/2/4/10915930/mozilla-firefox-os-internet-of-things
If those can consume web content via an engine or service that has a User Agent, it won't make it go away. Aspects like "is tablet?" or "is phone?" are just becoming more and more complicated and "interesting" ;-) Werner
