It won't happen because they have made a lot of money from it. Effectively rebooting the franchise guarantees Activision an effortless stream of money for old rope. And they will continue to have Bungie do this until Bungie either quits it's contractual obligations at the end of the agreed term or, if it hasn't happened already, what is left of the original Bungie team decides to sell the company to Activision and leave to reunite to start again under a new name. The latter seems more probable.