u/JackTheZocker

Considering the Knights are going to play each team once, they are probably going to face the Dragons last. To raise the stakes of that match, I predict they will lose their match against the Roses. Dragons and Knights will then go 2:1 into the final game for the title (other teams will all have lost twice by then)
Others have already pointed out the difference between Key's flames being red/orange before his "awakening" and blue afterwards, the blue flames likely representing his mother's tama while the red/orange is his own
A sixth member might join the Knights. The ice girl is a hood contender but seeing how she is with the Dragons, I wouldn't be surprised if the ghost girl joins now that she is out of the Shadows (in a nerfed form without the crown). Of course, her being a second keeper makes that less likely.
Seeing how the trainer who played with Key's mother (Noreen?) has been acting so far, I'm pretty sure she is the main antagonist and responsible for stealing the light kid's tama. She was mad at her team losing against him, and the way she is obsessed with Key's mother points at her being the villain
On that note, she is also likely responsible for the incident that killed Key's mom, trying to copy her tama too much and being unable to control the dragon
Not a prediction but just hope they are going to add some characters whose names I can actually remember or write from hearing.