I looked it up and it said that there should be a season 4 because of the fans and critics but they want to wait for official statements from the creators.
The series 3 finale closed all of the loopholes. now there were the Jana Bites, but I don't see the series coming back from the ending they gave. They'd need to get Maddy and Rhydian both back.
I hope so but Maddie as to say yes because she wasn't in season 3 because she want to college but everyone want her to stay if you don't believe me check in Wikipedia or Google.