Well, I wouldn't go so far as to say SSJ4. I merely stated that his involvement was at the beginning of the series, and SSJ4 is much farther in than that. I don't really have an airtight way to confirm my knowledge. Like you said, it's been debated endlessly. So I guess we're at a stalemate, huh? ^_^

All I can say is that, while I've never heard one way or the other whether Toriyama was involved with the Goku Jr. storyline, I CAN say with 100% certainty that it was a TV special and NOT a movie, since DBGT had no movies attached to it. The closest to a GT movie was the 4th DB 10th anniversary movie that was created during GT, uses more GT-ish character designs, and uses Dan Dan Kokoro as a theme.