May be. But IIRC the runes on Victarion's/Euron's horn were Valyrian or at least eastern weren't they? The horn of winter would more likely be encarved with runes of the children or at least in the old tongue. Also it says (if Moqorro is to be believed) that the horn is a "binder of dragons". Doesn't really sound like Joramun's horn.