Actually after celestia i think there's only gonna be one more world because since all worlds are based on a school, i think MB might be the myth world o: I know Marleybone isn't magical, but It wasn't always like that, in fact, in one of the history books, (chelsea court one) it says that MB was once a very wild world.
Please post and if you think i'm terribly mistaken, please don't be angry.
I think I read that they had wild tribes, and attacked each other, and then one tribe made piece with the other tribes, thus founding the faniciful one nation Marleybone. I think it could be any school at this point lol :D, but if you just look at the golems, it would be storm, if you where looking at cats, it would be random, and if you were dealing with those tribes, it COULD actually be myth. Don't get me wrong, I'm just guessing it COULD be myth.