Those are good suggestions, and not far off of what we've been thinking. I agree that there should be some kind of flag for new or changed material.
I think that there probably won't be a huge amount of updating. We do need to make some changes for the new IPTC Extended, now that it's in CS5 and LR3. However, it won't be until there are some new panels for earlier versions of Photoshop, so we don't have to do it more than once.
At the moment, the bulk of new material will probably be in the form of Workflow case studies, like the recently added Camera Scanning material.http://www.dpbestflow.org/camera-scan-workflow
Of course, there is also a related Best Practice page. http://www.dpbestflow.org/camera/camera-scanning
There's another possibility. I think we should be asking people to sign up for update notifications.