I love this game, I'm not trying to be a downer or take the fun away but realistically I don't think there is a layer 5.
The ending of Layer 4 just seemed like such a nice way to cap it off and the message from Billy even said this is one of the last things he's putting in the game before release.
I just think the Cheater ring is left over content from alpha that he may have had a plan for but just left in for fun to see if people could even get to it.
I just think the extra rabbits are just that: extra rabbits. Maybe he had plans for there to be more than 16 to get for the rabbit island.
Finally all the animals you can play the flute for in the walls are probably just for fun too. Maybe they had a purpose at some point but idk, I add stuff like that in my game that I'm developing, it's just fun to see if anyone will ever figure out how to get to it.
I would love to be proven wrong, it would be amazing, but I'm not very convinced there's anything more.
A ton of people dont know the original Pokemon Duel was an actual board game done by the Pokemon Company themselves. It was called the Pokemon Trading Figure Game, and it was released back in 2007, but due to lack of interest and complications with figure production, it was canceled only 2 years later in 2009.
There's a ton of interesting history out there about the TFG, like an unreleased expansion that some people got their hands on. You should definitely check it out.
TheJWittz made a great video a while back about it: https://youtu.be/d5WliMM2h6I?si=Oci-f3AlKgQMOGLX
Pokemon Duel Boardgame
pokemonduel