Retroactive Hextech Rewards for Mastering a champion

so, I'm not in this boat yet but to my understanding you get something for mastering a champion, which is why you cant get chests or keys with a F2P unless you own them, so my question to riot and anyone with the answer, do you get anything for champions you've mastered before hextech came out, if so will it be after hextech is live in all regions or will it be later. thanks Bones