I have to admit, I'm surprised they have no plans to migrate Firefox over to Servo. It seems like a waste, considering that desktops and laptops could both benefit from the increase in parallelism.
If (when!) Servo continues to execute well, plans for integrating more risky pieces will require more top-down planning than the bottom-up, grassroots work that is going on today. As much as I love Servo, even I wouldn't argue we should stop the world and move 200 developers off of Firefox onto working on it full-time for the next year. Such initiatives rarely go as planned.
Longer-term, we plan to incrementally replace components in Gecko with ones written in Rust and shared with Servo. We are still evaluating plans to ship Servo as a standalone product, and are focusing on the mobile and embedded spaces rather than a full desktop browser experience in the next two years.
From the article:
parallelism results in power savings. Multiple threads working in parallel on a page-rendering job allow the CPU to complete the entire page in the same amount of time while running at a lower frequency.
Also powerful x86 CPUs are so good at shared-memory multithreading (cache coherency, large caches) that x86 is actually the best case for us (which is not to say we're bad on ARM, of course).
Since Mozilla doesn't have the ability to fund advertisement campaigns the way Google and Microsoft can they have to be more careful about momentum and not waist growth opportunities by spending them on a established product which is consistently shrinking in marketshare.