Leave your game open enough so that you can add new armors, weapons, skins, vehicles, and classes AFTER the game launches.
I remember far too many "Awww man! That would be so cool to have in MP! Too bad we can't...." moments for the Halo series.
If you could also learn to Show and not Tell that would be fantastic too. (Reach)
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I'm gonna say that Destiny being an ever changing and expanding online world they want you to live in for the next ten years suggests they already have that bit covered.