I think Firefox OS has potentially huge geek (read: early adopter) appeal, which Blackberry and Windows Mobile do not have - they are dead. Tizen, Jolla, and others are just obscure specks. I am rooting for Firefox OS to be a serious contender within a couple of years. I think it has a strong chance to be #3. Likewise I don't think it has any chance whatsoever of taking the #1 or #2 spots - those are going to stay as…
Jolla has a better appeal I think. Firstly it's a full pledged Linux, not limited to JavaScript applications only. Secondly one will be able to run Firefox OS applications on Jolla as well, since the browser there is using Gecko.
I like the Firefox OS concept because it has a better chance at being popular amongst non-technical folks and because, even if it had like 5% of the market share and no more, even so it would bring benefits to everybody, including developers, including end-users - because those Web APIs are also pushed by Mozilla for standardization.