I too would like another installment with new characters and settings. Just as I suspect what Bioware intended for KoTOR - a stand alone story.
IMO , the problem with carry over characters and plots is that everybody would have very high expectations and hopes, that the finished product would have difficulty living up to. And also the main story arc of the game would have to revolve around pre-determined dictums set by its predecessors, making new and perhaps even more exciting plot directions difficult to execute.