I honestly don't think we'll see the change to a rolling type release until 14.04, there have to be many things put into place before that can happen, and I can see Canonical wanting to push Mir and Unity Next out the door before making the needed changes.

That being said, grahammechanical's method to start with is the only way to upgrade to the next version, when the toolchain is first uploaded. I haven't paid any attention to when an upgrade via upgrade-manager becomes available, but to me it normally doesn't happen for the first couple of months of the development cycle