Mozilla believes that there always have to be options
With Opera abandoning the fight, Mozilla is pretty much left all alone against the WebKit onslaught. Sure, there's also Internet Explorer but Microsoft isn't exactly the first name that comes to mind when thinking about the health of the Internet.And, even as WebKit dominates, Mozilla isn't giving up anytime soon and, because it makes more than enough money with Firefox, it won't have to.
Mozilla’s CTO Brendan Eich makes it very clear that Mozilla is not Opera and that switching to WebKit would not only be technically unfeasible, it would also go against everything Mozilla stands for.
Mozilla puts users first and users are not served by monoculture, while WebKit is great with web standards, it's big enough to do its own thing. At the same time, there are big conflicting powers within WebKit development, Google and Apple in particular.
“At all three levels of vision, strategy, and certainly execution, Mozilla has good reasons to keep evolving Gecko, and even to research a mostly-new engine,” Eich explained.
“The switching costs for us, in terms of pure code work (never mind loss of standards body and community leverage), are way too high for ‘switching to WebKit’ on any feasible, keep-your-users, current-product timeline,” he added.
In pure practical terms, switching would mean giving up on a decade of work and would take years to accomplish fully, this while the benefits of switching aren't so clear.
Most people couldn't care less what engine their browser uses as long as it works. Even among those that do care, even among developers, having one dominant engine doesn't seem like such a bad idea – in fact, it's for the best in some aspects.
But, as Eich explains, there is no “one” WebKit, implementations vary, sometimes to big degrees, so big that developers have to take into account which version of WebKit they're targeting. That doesn't sound like the “write once, work everywhere” heaven a single engine could mean.
Mozilla has a tough fight ahead of it nonetheless; it has the third biggest market share on the desktop and almost zero market share on mobile devices.