What could spielbergs Halo TV series be about?

So we know rougly what nightfall will be about, but what about Steven Spielbergs Halo TV series? My Idea of what It could be focused on is an ODST story. It could based on the game itself and the characters, or an entire different plot give me your guys suggestions and ideas of what it could be.

Would be really cool if it was focused on ODST. But it would also be cool if it was focused on the promethean