I agree, though there is so evidence supporting it, firstly multiple sightings of official merchandise with twilight as an alicorn, mistake? maybe, but the fact that it happened multiple times in different images makes that less likely. Also it is almoast certain twilight will become a princess (Will a very small chance its cadence), even if only temporarily. This is shown in the latest add, featured around twilight "Discovering her destiny" then finishing with said coronation title, the fact that there is not even a mention of cadence makes it seem very likely it will be twilight (Again not 100%). This whole princess deal is relevant because every princess up untill now has been an alicorn, and up until "the Magic Duel" hasbro even officially named alicorns "Princess Ponies" making it all seem more likely