WoW has nothing new added to it. The core game is very stale and they can only dress it up by raising the level cap. The sub numbers have obviously peaked a long time ago but the game will have a few more expansions in it yet.
I think MMOs have lost touch with the roots of RPG gaming.
What happened in the pen and paper days? You'd start a campaign/scenario with fresh chars, and would play to the end. Then you'd start a new campaign with new chars.
In today's MMOs, designers have become obsessed with making each campaign a continuation of the last. Thus they have to increase levels, etc, to the piont of sheer broken-ness.
And the only way to reset is to launch a new game. How silly is that?
Why not go back to the roots of RPG gaming. Release a new expansion where you can't just bring your max_level char, but have to start again.
The reason people want to rush through low level content when they re-roll is simple:
a) the perception, rightly or wrongly, that low-level content is boring or lacks challenge (lack of abilities, etc).
b) the story only really kicking in at high-level, or when raiding
c) lack of early game content - in WoW each new character would have to do the same areas again and again.
This is again different from pen and paper. The challenge can and does start from the beginning, and so does the story.
There is /no/ reason that the low-level game should be filler, or a big tutorial, or a stepping stone to the real content. Only the expectations of players and lack of developer imagination dictates this.