Earlier quoted context omitted.
I don't think Mozilla will ever switch. The reason why they've their own engine and try to keep a decent marketshare (which they do indeed have), is to be able to have a say on web standards, and the web in general. Having a say ensure there isn't a single voice taking decisions that led us to things like IE6. And we're actually starting to see IE6-ish stuff happening with webkit, as it's nearly the only rendering en…
I would think one vendor would be great for standards: it is the standard. It sucks for any kind of innovation, though, as IE6 shows incredibly well. Out if curiosity, what IE6-ish things do you see WebKit doing?
It isn't like WebKit is intentionally doing IE6-ish things, it's just that any rendering engine will have certain bugs. Developers try to work around these bugs, and if their is only "one" implementation, they'll start relying on its quirks. A good example in C would be storing a pointer in an int. It made perfect sense at the time, and it allowed people to be lazy. However it doesn't make any sense these days.