I assume you're referring to the 9-10MB placeholder file size on the PS Store (or Xbox store thing). Those were there before the releases of TDB and HoW as well. However when the 1.1 and 1.2 patches came, they were what 2-4GB? I don't remember why the system requirements said about TTK, but I think it was around 30GB? So we are getting at least 10GB of new assets and however much is getting replaced in from the original release. I'm speculating on the 30GB, as I don't remember what or if they said anything. But still, this topic has been floating around since November and its just a misunderstanding of the way the online store works.