It'll be a nice perk to have a secret level that gives a sneak peak into the expansion.
A dungeon for instance that is filled with mobs of levels 70-80+ where your chances of defeating them is quite low.
You'll need to be 60 to get there... and they don't drop gear. It'll be there just for amusement. You won't gain anything from it.
Bashiok owning Bluerevolution
Q u o t e: I hope you're an organ donor, because your brain will have to be studied until the end of time.