We've seen the addition of Cross-Realm instances in patch 3.3. My question is, in Cataclysm, will we see cross-realm raiding?
This was answered long ago in a Twitter Developer chat late February.
Q. Will there ever be cross-realm raiding?
A. This is something that we are looking into. There are a lot of design issues that need to be addressed before we could implement something like this, but we are definitely interested in the idea.
Q. Are there any plans to allow cross-realm raiding?
A. If we can solve the problems with it, we might give it a try. One of the problems is getting the group back together, especially on the longer instances. Loot drama and stuff like that is always a problem. There is also the ongoing concern about the concept of your realm having less of a sense of community.