Runescape's pretty old and will die out soon. I heard that if they wish to stay with the rapid growth of graphical capabilities, they would have to switch to a different more powerful language. The reason for Java at the begining was because I am assuming Jagex only basically knew Java as their primary language. Another good reason for Java is due to it's security if you listened to Security Now (with Leo Laporte and Steve Gibson), I believe episode 50. If they moved to C++ or Pearl, the game would be hacked in a matter of minutes do to it's popularity.