Capcom's finally beginning to detail a system that penalises players who quit out of online play after losing. Oh, and Guile will be April's DLC character. The latest update on Capcom Unity details the first steps that the publisher will be using to punish rage-quitters:
We're also happy to announce that we will be implementing a system to punish players who frequently disconnect during matches (aka rage quitters).
The way this will work is the system will identify players who have high disconnect rates during matches and will lock them out of matchmaking for a period of time. Players who have been identified as abusing the system will receive an in-game message notifying them they have been locked out of matchmaking. More additions and enhancements to this system will be implemented in the future.
You can find more details about the April update and Guile DLC here.