The fast forward solution

Blizzard has already started to tackle the problem of new players, and they did it by speeding up the progress of new players to level 60. Since patch 2.3 quests up to level 60 give more experience points, and you need less xp to level. Thus the number of hours to 60 has been significantly shortened.

The question is where we go from here. People who played the original Everquest will remember the term "hell level", describing levels in EQ where due to the complicated formula used to determine how many xp you need to level you suddenly needed far more xp to get to the next level than you needed for the previous level. Blizzard inadvertedly introduced hell levels into WoW. For a new player, who didn't spend many months at level 60, the current level 60 must appear like a hell level. He got used to leveling quickly all the way up to 60, and suddenly progress slows down significantly. You need nearly three times more xp to get from 60 to 61 than you needed from 59 to 60, while the quests and mobs do not give significantly more xp now (only item rewards are better in Outlands, of course).

Rohan from Blessing of Kings suggested to keep time to max level constant, regardless of how high the max level grows. Thus when Wrath of the Lich King comes out and sets the level maximum to 80, Blizzard would have to speed up leveling from 1 to 70 by as much time as it takes to level from 70 to 80, hopefully smoothing the leveling curve while doing so. The problem with that approach is that levels aren't infinitely compressible. Zones have a certain size, and you need a certain number of quests and time to see all the corners. If every expansion raises the level cap by another 10, we are heading towards a situation where you do less and less quests in a zone before you outlevel it. And the new levels added in the latest expansion would always be hell levels, being much slower than the way up to them, because you don't want to rush people through the new content, only through the old one.

But speeding up leveling is not the only fast forward solution Blizzard offers. The new deathknight class will not even start at level 1, but directly at a higher level, probably level 60. And apparently previous ideas of having to do a level 80 quest to be able to play a deathknight have been discarded, new players will be able to play a level 60 deathknight on their first day. Which then of course raises the logical question of why only deathknights? Time to max level could easily be held constant if new players could start any class at max level minus 20. That of course would make the existing level 1 to 60 content even more deserted and useless, but at least there would be a reasonable chance to find a group with your freshly created level 60 character right from the start.

If World of Warcraft is designed as a game where the fun and the social activity is by design concentrated at the level cap, it makes sense to fast forward new players to that level cap. The disadvantage is that you are losing something when you shorten all the old content, regardless of whether you speed it up or just skip it.