Honestly? I don't think the writers have taken John too much into consideration. Because if he broke? He was on his way to being a demon. And if he was on his way to being a demon, and not rescued like Dean was, how did he leave in the shiny light, thus implying Heaven?

Also, with the undoubted uproar in Hell over a gate being opened and demons doing their best to escape, anything could happen. There is fic to be had, no doubt.

At the point in time when John escaped Hell, I don't think the writers had thought as far ahead as we've gotten. I don't think they had any concept of how they were going to depict Hell. They didn't know that Dean was going to be on a rack. Neither do we know whether or not all souls end up on a rack, or whether or not all souls end up on a rack all the time.

I could be wrong, and if they tell me otherwise, I'll go with the story they tell. But right now, I don't see how a demon in training could have "gone into the light."

I honestly don't think, at this point, John's story matters one way or the other. What does matter is that Dean believes he fell short of his father's expectations, and that Dean was the one who broke the seal.

Actually, upon further reflection, I think for Dean's sake I'd like it if we learn precisely what happened with John. But honestly? I don't think the writers are going to give us the satisfaction.