That being said, I don't believe we will ever go toe to toe with Alduin. I don't see how they could make it different enough from a normal dragon fight, or have Alduin presented in any form that makes it actually seem like he could end the world, but still allow you to fight him.
The only thing I can think of is maybe Alduin cannot "eat" worlds, but that it is rather creative license given with the prophecy and stories of old. Perhaps Alduin could be responsible for the end of the world, in that he does some particular thing, such as a magical rite of some sort which enables some other cataclysmic event to occur.
In a story I wrote for a pen-and-paper RPG I ran back in the day (which I had been in the process of converting into a mod for Morrowind), the adventurers were up against an unimaginable threat that they could not possibly hope to defeat face-to-face. However, this power could only establish itself in the world through specific events, and basically had to be "invited" into the world through rites and summonings, and a specific sequence of events had to occur. Trying to stop these events from occurring was considerably more feasible for the adventurers than fighting a nearly omnipotent being head on, and it would accomplish the goal of preventing the destruction of their world.
Maybe this is similar to the case here?
Also, in the RIFTS pnp rpg, gods could never manifest their true selves in the world, only avatars which were much weaker. Killing the avatar did not truly kill the god, although it could take several millennia for them to reassert enough power to establish a new avatar.