I guess there still is enough theme cards to throw in for the character ace cards and some duplicates. Or who knows? Maybe they are planning for a level 20 cap at that point? But this also looks like they are at least considering the possibility that this game won't get that far.
it could be around longer if they stopped this speed duel bs and gave us an option to play the real rules, so we could have cards that would be unusable in the speed duel format (like burn or cards that need more space on the field)
Most of Ishizu and Zane's Cyber Dragon cards are in boxes. A characters cards being in boxes doesnt disqualify them. Look at how they gave Scud a bunch of filler cards for level up rewards, they can do this for any character if their cards are already in the game and the demand for that character is high.