Whatever we decide to do, we won't be porting Firefox as we know it to iOS, unless Apple makes major changes to their App Store policies. The principal issue is that on iOS, the only software Apple allows to download content from the Internet and execute it is their built-in iOS Webkit component. Under that policy, every browser --- including iOS Chrome, for example --- must be some kind of front-end to Apple's Webkit. Thus, from the point of view of Web authors --- and users encountering Web compatibility issues --- all iOS browsers behave like Safari, even when they are named after other browsers. There is some ability to extend the Webkit component but in most areas, engine performance and features are restricted to whatever Safari has.

I certainly support having a product on iOS and I don't necessarily object to calling it Firefox as long as we're very clear in our messaging. To some extent users and Web developers have already acclimatised to a similar confusing situation with iOS Chrome. It's not exactly the same situation: the difference between iOS Chrome and real Chrome is smaller than the difference between iOS Firefox and real Firefox because Blink shares heritage and still much code with Webkit. But both differences are rapidly growing since there's a ton of new Web features that Chrome and Firefox have that Webkit doesn't (e.g. WebRTC, Web Components, ES6 features, Web Animations).

In the meantime I think we need to avoid making pithy statements like "we're bringing Firefox to iOS".

http://robert.ocallahan.org/2014/12/we-arent-really-going-to-have-firefox.html