It shouldn't fragment WebKit development much at all. WebKit2 is just an API layer on top of WebCore, much like the Qt and GTK WebKit API layers. Most of the work is done by WebCore, which is shared by all the API layers.
Statistically speaking, our crash rates have been going down with each release. However, there are, of course, always more crashers. If you'd be willing to help us diagnose the issue, we'd be appreciative.
http://trac.webkit.org/wiki/WebKit2 http://dev.chromium.org/developers/design-documents/multi-pr...