Beware the smiley face! =D
I'll make this quick.
Now, there is a chance that MC wont be the main character in Reach and we probably wont see him leave the planet and lead into Halo CE.
Wouldn't it be great if this bonus download gave you an extra level or something where you are the Chief and you make it off Reach (I'm not sure whether this was described in the Fall of Reach as I havent read it. Oh no! Ive got an idea for a bit of storyline even though I havent read the book! Sue me!)
Either that, or just have a Legendary ending where we see the Pillar of Autumn arrive at Halo.
K =D