Have not heard anything for sure.

With Burning Crusade, they changed the 1st-60th requirements to be 30% less experience per level.
With WotLK, they did the same for 61st-70th, by the same 30%.
I'd guess Cataclysm will reduce the experience requirements for 71st-80th, but that is a guess.

Blizzard has stated in the past, part of their design goal is for 90% of the player base to spend 90% of their total time in game, playing at maximum level.
The leveling up is not necessarily easy or instant, but its a lot quicker and easier then almost anything else in the genre.