I wonder if they'll remove (or at least most of it) developer tools from the main browser and try to get developers to use this version. Common criticism of Firefox these days is it feels (and in most cases is) slower and more bloated than Chrome. This move could help Mozilla make FF faster, no?
Well, the main advantage that Chrome has vs Firefox is not speed (these days, Firefox is faster than Chrome on most benchmarks I have seen), but smoothness, which is largely due to the multi-process architecture of Chrome.
Developer tools have strictly no influence on this, and the multi-process version of Firefox is currently being tested. I don't remember whether there is an ETA.
To me it looks like speed is one of the major advantages. JavaScript speed is only one thing. There is also render speed. E.g. this runs totally smoothly (with a bit of flickering (z order problems?)) in Chrome: http://keithclark.co.uk/labs/css-fps/nojs/
In Firefox it seems to have something between 1 and 5 fps and is totally glitched out.
JavaScript speed is not what needs to be worked on currently. Render speed is.
