Clearly you do not understand. Let me make it a bit more clear to you. We went back to Outland on a quest line to see a few visions. This had nothing to do with the zones themselves or anything going on in the zones. We then went to the Black Temple and remained there for the rest of the quest chain. What the OP wants is an entire expansion focusing on the entire continent of Northrend. Not just a few small quests here and there that send us there for something (pet battle dailies anyone?).
Does that help? He wants an expansion based around going Back to Northrend. Not a few quests. We did not go back to Outland while it was being the focus of an expansion again. We only went back for a few quests.
See? We did not go back in the same way that the op wants to go back to Northrend. It's probably a good thing you didn't read the rest of the post. Probably wouldn't have anything intelligent to say about it anyway considering this response.