If two of the Sonic cartoons can be as good as they were (or are, in the case of Snic X), there's nothing to keep a Jazz show from working. Other games have done well in animated form as well. In particular, the new series based on Gungrave is wonderful.

As for the chance that the show will be "kiddy"... on some level, you are probably right. But then, it would be labeled that way no matter what. The majority of the TV viewing and game-playing public is going to automatically assume "kiddy" as soon as they see brightly colored fuzzy animals as the main characters. That's including any future Jazz game too, not just a cartoon. We'll just have to rely on a younger audience as the "fuel" for the fandom, and the "mature" gamers who are actually mature enough not to be afraid of cute animals will come along too. That was basically the idea in Jazz 2, or the game wouldn't have been so easy.