Initially Blink will be using the same code base as of WebKit but, over a period of time it will diverge into a totally separate project. Google and Apple are seemingly in good terms when it came to programming at least and with this fork, this long time cooperation is set to end. Up until now Mountain View and Cupertino were contributing to the same code base of WebKit but now each company will be treading different paths while adding new features and supporting new standards as they deem fit.
A fork and that too in a browser engine would probably cause quite a lot of unrest on the web but, Google is all set to take the plunge as it believes that it will be good to have multiple renderer engines as there are multiple browsers. Multiple rendered engines “will spur innovation and as time passes improve the health of the entire open web ecosystem.”
Google already has a short term roadmap in place and the initial work would be focused on the architectural improvements as well simplification of the code base. Google notes that they will be able to remove 7 build systems and get rid of over 7000 files. These files house more than 4.5 million lines of code which Google believes once removed will allow for the code base to be healthier in the long run with more stability as well far too less bugs.