Although a session/panel/discussion on this is scheduled for later today, I wanted to capture some thoughts from the BOF yesterday on Sakai 2->3 migration.
The old idea of "hybrid" mode is still going strong - in fact, it's really the only idea going for transitioning users from one to the other. We're still operating on the idea that we can run Sakai 2.x "headless" and show Sakai 2.x tools inside of a Sakai 3 container. However, my concern is that at some point, there has to be some mapping and migration from a Sakai 2 tool to a Sakai 3 tool.
User data that relates to a particular instance of a course in a particular semester is not so important - although we have an obligation to retain that for a certain period of time. The data that really does have to be migrated to Sakai 3 tools is what Lance called the "structure" of the course. By that, we don't mean the particular layout - which would obviously be pretty different in Sakai 3 - instead we mean the content, but also the assignments, and the forum topics (although not the posts themselves), etc: anything an instructor would need to bring over to teach the course again to a new group of people.
Could we migrate this data piecemeal based on Instructor course copy? That is to say, when an Instructor is ready to teach a course in Semester B, and they want to copy old content from Semester A (we already have this metaphor in Sakai and Blackboard), the course copy process will migrate any tools to their Sakai 3 versions if those tools are available. For the other tools, Sakai 2 versions will be nested inside.
And then, when the Instructor is ready to teach Semester C, she initiates another course copy (from B->C), and now any remaining Sakai 2 tools are now migrated to their Sakai 3 equivelents (which are now available).