I would assume so, though you could go either way with the lore. If Larian wanted him to make an appearance in Original Sin, I think he would have to be motivated then to go on a long journey somewhere, to get him outside the realm of Rivellon. Either that, or have him die in Original Sin (of old age and/or some kind of heroic sacrifice). Just making an appearance and not having an explanation of why he made it 8800 years and then disappeared somewhere during the next 1300 would leave an obvious and unnecessary plot hole.
I don't think there needs to be a dragon involved in Original Sin, though, unless it is to show them being withdrawn, or withdrawing more, from the affairs of the seven races, and dragon knights not being directly involved in Ferol. Now for an RPG about dragon knights I'd have the D2:ED hero, Patriarch and the Dragon Commander all involved. Personally, in a turn based isometric game, I don't need to talk to a near deity who isn't going to get involved (at best providing some limited help or information) and isn't going to turn my character into a dragon knight.
