Once upon a time, SE mentioned something about reserve exp points. Not really sure what their plans are with them now though. When they first changed the exp curve, I gained a level or two - but then again, I wasn't capped either.
What SE mentioned about 'bonus' xp has nothing to do with the level 50 cap, it has to do with extra xp gained while you are fatigued. When you hit 50 you're xp earned does nothing. But what did you expect? You hit the cap.