User blog comment:Jack Pistol/Immortal Dovahkiin?/@comment-2040576-20121002202215/@comment-2040576-20121004102707

Very interesting points...

I like the second possibility given, about Alduin being a greater being than the Dragonborn.

Perhaps there is some time mojo working on Alduin and when defeated by the Dragonborn in Alduin he either fal back into the midst of time or some other plane of existance, which is how the other dragons noticed his lack of existance. That or the Aedra/Daedra are intervening as I think you are hinting (mainly towards Akatosh) :P

I like the DLC idea. To add to your on-going conversation above, maybe defeating Alduin would necessitate the revival of a second Dragonborn, to overcome his greater existance. Either the two Dragonborns work together and rip his soul apart when killing him (it can't go just one way, it would have to split due to two beings try to absorb it, perhaps?) or (sorry going back to my ridiculous idea of absorbing another Dragonborn's soul) their combined life-force deems them greater than him and thus they are able to absorb his soul.