No, it won't. People will buy premium buildings anyway, for various reasons (such as looks, or different footprint that better fits one's city). Example: Forge of Empires. Some event buildings are better than Premium ones (or at least very close to Premium ones) and people still spend Diamonds on Premium stuff. Keep in mind that in FoE you have two items that allow you to upgrade event buildings: One increases the Age of the building by one, the other increases the Age of the building to your current Age, no matter what the previous age was.
FoA's Ages are the equivalent of Elvenar's Chapters, in case anyone's wondering.