It's okay. He'll just tap into the highest Light Side of the Force power of being able to communicate to us in spirit form.
http://www.youtube.com/watch?v=ZkjEB63qSeQ
Excellent point though Ric. There should be tenets in place that allow this thing we're all a part of to continue thriving, growing and developing regardless of the "moving on to another plane of existence" as you call it or "death" as I like to call it.
On Zog's point of the fragmentation of JKD once Bruce Lee died, I just would like to add that I'd bet my left testi that Bruce would totally be a 10th Planet warrior if he was still alive today.