As a hardcore PVEr one of my chief interests is mainly in WoW Cataclysm raiding and the new dungeons that comes with the expansion. Blizz has promised us at Blizzcon that there will be more end game content than ever before, but considering the list of potential instances I’m not sure this will really be possible. Would look forward to a Cataclysm guide to raiding but a lot could change before the release but right now they have announced eight five-man instances and five raids. In comparison Burning Crusade had fifteen five-mans and nine raids and Wrath had thirteen five-mans and eight raids. So clearly Blizzard is planning something else.
The simplest solution is that Blizz hasn’t released all of the details of raiding and there are many others in the wings. This may be what happens with five mans especially since we have seen four new ones implemented in Wrath since its release. With raids though I doubt this will be the case. Raids are so huge and require such delicate balancing for progression the developers can’t just say “Hey, lets go make a raid full of murlocs!” (Although that would be beyond awesome.) Instead I have a theory that Blizz will stop with huge linear raids like Ulduar and instead move into much smaller winged versions where much of the content is optional. A map of the remade Black Wing Layer raid shows a large circular hallway with many side rooms, each probably containing a boss. While you may need to defeat X amount of them to unlock the final boss you will have many more options for which path you want to take instead of just killing boss A, then B, then C. Other options may include adding additional raid bosses as time goes on like the Vault of Archevon in Wintergrasp or many more single boss instances like Magtheridon and Sartharion. Of course, this is all conjecture and theorizing. But I believe that with WotLK Blizzard finally figured out the formula for a successful and fun raiding environment.