Riot, will we ever see Reward Skins?

I understand that making skins for champions take time and you want monetary compensation for the time and effort that went into those skins. I understand that completely. But I was wondering if there will ever be unlockable skins.

I see them as simple recolors or simply reverse colored skins. They could be earned after winning X number of games or getting X number of kills with a champion. It is always nice earning something rather than just buying it. That is why so many people try to get to Gold in ranked. You earn an awesome skin that no one can just buy. It sets you apart. It makes you unique.