It's not so much the wings that bother me, but her becoming a princess. Simply slapping wings on her changes very little, but becoming princess changes the entire dynamic of the show. That being said, I'm not too worried about it, there's some neat things they could do with this plot twist. One thing they could do is shift the focus to entirely new sets of characters for Season 4, while still giving the original Mane 6 significant roles in the storyline. For instance, Twilight could be the new Celestia and take on a student of her own. Rainbow Dash would be the public face of the Wonderbolts now instead of Spitfire. I think that could be an interesting direction for the series to head in that would keep the plot fresh by adding new characters with different personalities from what we've seen while allowing existing characters to get further development through new roles.