Do you think the Zatch Bell! franchise will ever be expanded upon?
But I think an interesting way that the series creator (Makoto Raiku) could expand the franchise is make a prequel manga series and a sequal manga series.
Like have the prequel manga series take place 1,000 years before the current mamodo (demon in Japan) battle for king took place. Like have the prequal manga series take place in the year 1001, and have it be about the previous battle that happened before the current battle.
And for the sequal series, have it take place 1,000 years after the current battle took place, and have it be set in the year 3001. The human world in the sequal series could be very futurastic. The sequel manga series would be about the next battle that takes place after the current battle.
A lot of franchises like Naruto, Shaman King, Yu-Gi-Oh, Dragon Ball, Pokémon and many others have all gotten expanded upon with prequals and sequels. And I think it's not fair that Zatch Bell! may never be expanded upon, while those franchises did.