They won't fix it and here is why. The System of LoL doesn't focus too hard on rage quits cause they like to look on the bright side of it assuming that the rage quit was actually a DC or a Fail Connect witch their client "Fixes" have been making worse when they say it should make it better. All in all the Rage Quit Community will stay unless they actually find a way to determine otherwise.
Edit: The only actual way people get banned for rage quitting is if they are actually dumb enough to say "I A League Player Am Force Quitting This Game Ruining It For You All Because Of My Own Opinion On What I Think Is A Lost Game That I Wish Not To Take Part In So GoodBye All"