Krzysztof Kowalczyk:

Apple is in a tight spot. Suddenly WebKit will be getting 50% less code.That’s a big drop.

Which is why Apple is in a tight spot: if WebKit suddenly looses non-Apple contributions, they’ll have a hard time catching up with Blink. And while they really don’t care if web technologies advance quickly, they’ll be forced to at least keep pace with Mozilla and Google, both of which are putting the foot on the pedal recently.