The news of today will fade into 'morrow. They are the strong, they'll survive!
Could we possibly use some common sense? I'm getting flashbacks of Halo Wars' pre-release 'Will MC be in this game?' gibberish. To reiterate on what has been said, Master Chief is currently in slipspace during the events of Halo 3: ODST, and I seriously doubt he would show up at the tail end as a falling "comet". Would it be cool? Perhaps. But if you've a longing for the Master Chief, then just play Halo: CE, 2, and 3.