From an insider source at Mojang I've heard that 10.0 will feature zones and story and that it'll come after SL is finished.
Some of the zones will feature both quests and mobs
You will be able to level in the zones
The quests will have a story
There will be 38 bosses on release, all just slighly different variations of uunat
Bellular will be given a prominent role as a part of the new doomsayer faction leader
Stay tuned for more breaking news