Begin your speculations, Bungies new game Destiny looks almost certainly like a Marathon sequel or spin off:
"The document sent to IGN, and also to Kotaku, says that the game is set on a future Earth where, after a brief colonisation of the stars, humanity has been attacked by aliens and forced back to a single city on our home planet, where we are protected by a large, mysterious spacecraft. Another alien. Only this time it's a good one.
Players will take the role of what's basically a space knight, travelling the stars, exploring the worlds and of course fighting the alien menace."
http://kotaku.com/5963807
Info is confirmed by Bungie. Concept art looks gorgeous, but I'm sure people are going to be talking about this one in piece for quite some time: http://img.gawkerassets.com/post/9/2012/11/planet_1.jpg
K'lia?
Humanity fighting off a more advanced alien race for hundreds of years with only the help of one alien planet/spaceship? This is exactly where M2 left us off, a hundred years or so on. And basically the storyline for Eternal and Rubicon.