Sunwell Isle
Sunwell Isle will be located off the coast, north of Silvermoon, and will be patched in with patch 2.4
Sunwell Isle will be a major questing hub with a 5-man Normal and Heroic Instance (Magister's Terrace) and a 25-man raid (Sunwell Plateau). The goal with Sunwell Isle is to close the Burning Crusade storyline before the release of the next expansion.
There are still a few scenarios left that could be released to provide the players with more content if WotLK gets delayed for any reason.
At the release of the patch, players will access a small expedition camp where they can start questing. However as the questing progresses, players will expand the camp and make it grow to a small town by retaking building to the enemies (running daily quests mostly). You can consider it as a AQ Gates opening event, the more daily quests that gets done, the faster the whole server will progress.
The quests will end the Tempest Keep story arc.
"The Shattered Sun Offensive" will be the new faction of this quest hub. It also seems that Aldor and Scryers will finally start fighting together against the new threat.
Both 5-man and 25-man dungeons will be accessible from the start, but some bosses will have to be unlocked by running the daily quests (server-wide) and/or leveling your reputation. The 5-man instance will most likely requires Honored reputation with The Shattered Sun Offensive, the first three bosses of the 25-man instance will be accessible from the start, while the three last ones will have to be unlocked through questing.
Sunwell Plateau
Kael'thas will be one of the boss of the 5-man dungeon, he's still alive and he's now got a huge green crystal etched to his chest.
Kil'jaeden will be the final boss of the 25-man instance. The other bosses include Brutalicus, a giant Pit Lord who has lost his wings, Kalecgos, a blue dragon enslaved by Kil'jaeden, a Fel Dragon, the female Eredar Twins, and a Dark Naaru.
The 25-man instance will be slightly harder than Black Temple, and is tuned for Tier 6 geared players.
There will not be any "real" Tier 7 set, but some of the drops will be set pieces (not necessarily class specific). The drops quality will be above T6.
Daily quests
Patch 2.4 will raise the cap of Daily quests allowed in a day from 10 to 25.
PvP
Balancing actions will be taken in regard to PvP for certain classes.
Blizzard have large plans for, and they will be aiming to bring it closer to e-sport acceptance.