Future
The unannounced feature will be in the last patch of the expansion and give players a lot of new content to play with.
Proving Grounds is still being worked on and will be added if it can be done well.
Hopefully we will continue to see a new patch every two to three months, continuing to alternate with raids and story.
For Mists of Pandaria the quest team originally wanted to do a class quest for every class, but it would have taken as much time as doing an entire zone. The choice came down to doing Townlong Steppes or class quests, and the content that everyone could enjoy won. We might see more class quests for just one class at a time in the future.
There will be no heroic Ragefire Chasm, but the experiments down there will come in to play in the near future.
Going to Northrend is going back in time as far as Dalaran goes. Present day Dalaran is in motion, but it may not be reflected in game.
The team is being organized to try and avoid having a really long final patch before the next expansion.
Gamebreaker
Old age killed Lei Shen the first time he died.
The dinosaurs came from the islands in the South Seas.
Patch 5.3 will focus on how the events in Pandaria have changed the factions back in Azeroth. After that, there is a coup within the Horde, the previously announced Siege of Orgrimmar in Patch 5.4.
The seventh Sha will eventually be revealed.
No hints relating to if Ra-den dies at the end of the fight or not, so we have to wait for someone to get that far.
The Titans are more interesting when they are cryptic.
There may have been too many cutscenes in Cataclysm, so now they are reserved for the bigger events.
Lor'themar Theron was mentioned as a potential future warchief.
Draenei lore and story will be revisited at some point in the future hopefully.
The stories being told need gameplay to go with them, so they have to pick and choose what will be the best choice for the more rapid patch releases.