They will never completely get rid of rage quitters, there will always be situations where one poor soul won't be able to take his loss.
Yesterday I've played a bit of ranking for the first time in a few weeks. Met an ultra-silver or gold Nash (I only remember he had just around 4k LP) who beats me closely -- I'm only sitting at around 2200 LP at the moment because I rarely play online. Sure enough, he doesn't rematch me. The very next match we are matched together again, and I woop his ass cleanly. This time he takes the rematch, beats me, and on our very last set we are both down to our last sliver of health in the last round. We are a whole screen away from each other, so I decide to go for it and bait him into doing something stupid by charging up a clap (I'm playing Laura): sure enough he tries to somersault it on reaction, but I have more than enough time to recover and block it, letting him fall to his death on my fireball. And you guessed it, all of this was promptly followed by a rage quit on his part.
I don't even blame him, surely he was pissed, and didn't want to lose +100 points on this, but yeah, Capcom will never get rid of the occasional rage-quitters like this one guy in this particular situation.