I believe this is an honest move. This is what happens with software. Goals change, old code and design no longer makes sense, you refactor or rewrite. The architecture of WebKit was created to address goals that are a decade old now. The multi-process nature of Chrome alone, an amazing achievement and really quite elegant if you've looked at the way they bolted it on, was bolted on all the same.
One has to wonder if Google will be recruiting other WebKit contributors (RIM, Intel, Nokia, etc) to move over to Blink. This would put Apple in a tough spot.
We're going to be even more transparent than we currently are, actually, about how things get added to the platform http://www.chromium.org/blink#new-features. I'm pretty excited about how that's going to play out with regard to sharing ideas and implementations.
I'm honestly quite hopeful, both about Blink, and about WebKit.