I'm pretty sure Terry appeared as a cameo in Loeb and Ed's Batman/Superman run.
He did, that's why I don't want to see Ed McGuinness draw him again.
If Paul Dini was in charge I would like it to be semi cannon.
Yeeaahh...I suppose you're right.
A lot of Dini's recent run on Detective was sort of 'expanding' or re-writing episodes of the Animated Series. The Riddler had reformed (just like an episode of the 'toon) only, instead of his capture taking place at the end of the issue, he went on to become a private detective and featured in loads of stories (most of which, were great).
Also, Harley was released from Arkham in one of his stories (again, like an episode) and we got to see even more of her backstory (including a very nice little story about her first meeting with the Ventriloquist).
Basically, what I'm getting at is that most of what Dini did for Detective was just subtly improving ideas he had already had for the animated series. If he could do something similar for Batman Beyond, I'd be on board straight away.
The big problem with continuity and canonicity is of course
Return of the Joker for a variety of reasons.