To talk about D&D, even the game, that shuold be infinite, endless, limited only by imagination, can be un-immersive after you play 100+ campaign. Just look at metagamers, they suck all the "fun" and immersion out of the game. And you know what happen? The GM need to bring on the table all of the most strange, god-powerful enemies, because common bandit can't survive a gruop of metagamers/veterans. (for example, i still play D&D and i tend to play for fun, avoid meta builds, and going for underpower composition, it's way more funny then fight dragons all day long).
This is the same thing happening in WoW. We can't be anymore the kobold's salyers, and Blizzard give us Gods, Titans and so on.
But, this is not a bad thing, if you think the game, the player and the characters are more then 10 years old. It's just natural.
I think that some players now want to feel more "challenged" then immersed. But i can be wrong. Again, of course everyone wuold agree that feeling the first time immersion wuold be great, but the ones who use logic, knows that it's impossibile, unless, like you said, Blizzard came up with a brand new game.