And Kenobi survived until old age and then going to the Death Star. So who says no other force users survived to old age. Just because they weren't in the battle doesn't mean it's not true. Funny how that works both ways, huh?
Because even after the initial Order, the Jedi were still hunted down even if they weren't in the battle? I ain't saying that some Jedi couldn't survive, but we don't need a whole lot or some just appearing from thin air. There have already been 4 jedi that survived long enough, to join Luke's order..which is fine, but I don't think we need more then that.