How about having savage mode dungeons for 4.0. Since there will be leveling dungeons for the 61 to 70 levels why not take all those dungeons and make a savage mode for level 70 of all the leveling dungeons

savage mode would have,
-eveything has more hp and does more damage
- Trash mobs that are hard and can kill you if you don't stun their abilities dps it down fast.
-bosses that do so much damage that you must use cooldowns have really good healers
-party wipe mechanics and 1 shot moves
-enrage timers
-more complex mechanics from bosses then when you were leveling

savage mode dungeons could drop gear almost on par with savage mode raids but not quite as good.