Are you sure you're not trying to enter the "other" Ironforge Exchange entrance that is for one of the betrayal quests? It's labelled as Ironforge Exchange also, but you won't be able to get in unless you're doing the betrayal quest. The "real" entrance is behind the big huge mansion by the Elddar Grove zone where the Haunted House quests were for Hallowe'en.
That said, the Ironforge Exchange is looking at a relocation and expansion into some more convenient real estate that has fallen vacant. Once the banks finalize the purchase and the re-zoning permits are approved by the Queen, there will be some significant changes coming to the area.
LINK
(DominoDev) Re:Entering Ironforge Exchange
