The idea is that, Webkit will have to keep up with the innovations in Blink, and maybe even try to innovate themselves, to maintain marketshare.

This is assuming that Apple cares very much about browser market share. They're not really a web company, they just need a decent browser to include with their OS. Nothing stops them from switching to Blink (or Gecko) and letting someone else spend the money building a competitive browser that they can just include for free.

Apple cared enough to start the WebKit project. Though admittedly, ALL the browsers for Mac OS X in those days sucked.

And that's the point. They care to the point that their operating systems continue to have competitive browsers available... but now they do. Why keep throwing money at it once you have what you need when others are willing to pay in your stead?

Just like IE6 had to catch up to stay in the market, and thus could not hurt the web? :) And installing an alternative browser was easier on Windows machines than on mobile devices.

It doesn't even matter who will be the leader - if Apple leads, Android users will lose; if Google leads, Apple users will lose. Except if people start to buy smartphones based on the HTML rendering engine.

Except the assumption here is that improvements must necessarily be slower. But that's not necessarily true: collaboration between Chromium and WebKit was already incredibly problematic and was definitely slowing people down (http://infrequently.org/2013/04/probably-wrong/).

So there's a tradeoff--you're splitting people's efforts, and that's bad, but you're also removing pain points that slow down development.

Ah, gotcha. So what I'll mourn for is not the world of four days ago - but the world before Chromium and WebKit2 had split in the first place. :)

Webkit's done plenty of innovating, haven't they?

That was with help of google. Google had incentiv to work on webkit, not anymore. Now webkit folk are on their own.

Apple was doing enough innovating befor Google joined in: canvas element, CSS animations, transitions and transforms, etc., etc.

He didn't say the Web wouldn't be affected; he said it wouldn't suffer. And it won't, because it forces the WebKit (and Gecko) folks to keep up with Blink, and the Blink folks to keep up with their keeping up. Everybody wins.