You don't really wanna kill Tenpenny until you've got and done the You Gotta Shoot Them In The Head quest because he is important in it and once you complete the quest you get to get the T151b power armour. Though through Operation Anchorage you can get a winterized version which is nigh on indestructible. However to answer the initial question. No Burke does not ever re-appear in the game should you not take the opportunity to kill him (warning, Megaton can become very hostile if you do kill him there and surrendering is not always possible, even if you fire to save Simms) Even if you blow up Megaton he only appears during the quest so far as being on Tenpenny's balcony during the explosion if I remember correctly on the evil end to the quest he heads off on a request of Tenpenny taking him outside of the game domain.