Could this potentially be a first step towards eventually replacing Gecko with Servo? If Firefox (the application itself) eventually resembles browser.html [1], swapping out Gecko for Servo would be much easier.
That's not the primary driver of this plan. But it might be a happy side effect.
Servo is still in early stages, we aren't making product plans around it.
- currently browser.html runs on top of a gecko runtime (called graphene) which is based on the one we use for FirefoxOS.
- getting gecko to work on gonk is not different from adding support for other platforms like linux/mac/windows/android. Basically you need to provide implementation for low level windowing and input events. On non-posix systems there's a bit more to do in the nspr library, but that's not the case for gonk.
- we already have a port of servo that runs on gonk.
FirefoxOS has been using a 100% html UI since about 4 years, so it has been leading the way here.
Gecko and Firefox are quite intertwined. Even if we ignore XUL/XBL, there are things like XPCOM which are still deep-rooted. While this brings us a step closer to making Servo a drop-in for Gecko, this is not a step in a direction we're particularly interested in. At least not now, not that I know of (I'm a volunteer on the Servo team, as such there may be internal plans I'm not aware of).
For Servo one potential way ahead is bringing browser.html up to Firefox's level. Not the other way around :)