I just want to add a datapoint to your "where it's going to be" point, which I agree is the way to go for RIM.

Out of the blue, our startup started to receive suggestions directly from RIM on how to improve our performance and compatibility with the Playbook's Webkit implementation. They actually went as far as cracking open their web inspector and doing some analysis of our handling of touch events, some minor CSS issues (we use a lot of -webkit-transform), etc. I'm not sure whether this is part of an officially-endorsed policy or whether it's just some proactive folks within RIM, but it's been quite helpful.

Whether positioning the Playbook as a really good Webkit runner will win them back significant market share or not is up for debate, since there are many tablets entering the market that have decent implementations on decent hardware now.