What Ever Happened To Master Chief?

At the end of Bungie's Halo 3, you see the ceremony of all those that were killed during the battles, and Spartan 117 is one of the names. But if you beat the game on Legendary Mode (hardest difficulty) you see that Master Chief ACTUALLY survived in the ship, and it showed him go to sleep in a rest chamber, as he drifted of to a nearby planet. So, is Bungie planning to do something with Master Chief in future games? Only Bungie knows the answers to that.