I'd point out that there's a Fairy gym leader according to the so-far-accurate leak, but that stopped neither Lance nor Iris, soo...
I thought it was confirmed the 4th Gym Leader uses Fairies... But okay.
I wouldn't be surprised if the Champion uses Fairies, though Lance was the Champion in the generation that introduced Steel and Dark, so... likely not. Going with the theory that Viola's sister is the Champion, probably Bug, which would be a very interesting twist.
Playing) Fire Emblem: Awakening, Guild Wars 2 Waiting) Pokemon XY