Why kill the goose? (iPhone 5)

Every one is talking about the new iPhone or what they are calling the iPhone 5 (which I doubt that name) release date, and if you are wondering if there is a new iPhone well there is nothing for sure but as any other product it must be upgraded, back to the subject I say there is nothing in the market now days or even coming in the near future that will kill the iPhone or even comes close to the current one! so why would Apple brings out a new iPhone! Until this current day it is not easy to get an iPhone4 in some parts of the world and sales are shooting in one direction, up! Yet, Apple still have not released the white version of the iPhone4 which will increase sales, and I’m not even counting the iPad or the other products here, now put your self in Apple CEO shoes, if you are getting golden eggs every day, why kill the goose?