Some of these will come with the expansion, some will be in patches. Either way, they will be awesome and provide new depth to the game. Most of what I'm writing is the lore and story that goes along with each instance since not much is known about the actualy mobs you will fight there.

Medivh's Tower Karazhan- For those of you who don't know who Medivh is, he was the one who was possesed by Sargeras and initially opened the portal for the orcs to come into Azeroth. I'm not really sure what the point of going here is going to be since Medivh is good now. Maybe there is some other point of going in there we don't know yet. Who knows, only time will tell.

Kel'Thuzad's Place (Again, forgot the official name)- Not much to say here except this will probably be a raid instance seeing as Kel'Thuzad is one of Arthas' main assistants and has control over all of the plaguelands. This will be a very satisfying instance.

Black Temple- This is Illidan Stormrage's home in outland. No one has ever really known which side Illidan has been on all these years, but according to Malfurion, after Illidan lost to Arthas in that duel and the Frozen Throne it drove him to madness. To quote Malfurion, "I am afraid that the loss to Arthas proved to be his breaking point. Madness has embraced him. he replays the events in his mind a thousand times per day, but in his mind, he is the victor and Arthas is utterly defeated. He is too far gone, old friend". That about sums it up right there. Illidan has always been my favorite character, but atleast I'll get to see the new character model of him before we kill him. Sorry pal.

Caverns of Time- This will allow players to go back in time and relive some of the epic battles from the previous Warcraft games. Blizzard hasn't said what battles there are going to be, but I can see this having a few at launch, then Blizz adding more battles periodically.

While we know that these are instances, we don't know the number of players required to beat each one. 40 man? 20 man? 10 or 5 man? Or something completely different, we don't know. If you want my honest opinion, I think that the Black Temple will be a 40 man raid harder than anything else in the game.