Um...no there is a lot of things in the games that support Kanto and Hoenn being at the same time, you just don't acknowledge any of it cause you don't like the idea. Yes Steven makes a comment about the Hoenn Protags. It was a reference, the same things you used to justify music as a coincidence. If it wasn't a reference he wouldn't have said that. They also wouldn't have included the Lanette/Bill work, nor would they have acknowledged that Bill and Lanette were co creators of the PC System.
Its more fan speculation with little to no support that Hoenn comes after them in the time line. Why would they make a game that is so far in the time line so early? Why were the new Special Pokeballs that were invented in Gen 3 still in Gen 4 if Devon Corp hadn't invented them yet? Why was scott Searching around the world to test his One of a Kind Facility if there were other versions in Kanto and Johto? Yes Scott Opened the Battle Fronteir in Emerald, it wasn't opened/finished until Emerald's Post game. There are many facts from the games that support its placement with Kanto or between the three year period between Kanto and Johto.
Steven is still the Hoenn Champion meaning Wallace is a Gym Leader, so they are following Ruby/Sapphire story if Steven being in the World Tournament is any reference to Hoenn games. We've been told to stop discussing this in other threads, so lets stop please neither side is going to accept the other, all major sources have Kanto and Hoenn at the same time, so unless Gamefreak comes out and says that Hoenn is in the future it isn't.
We know that all the Gym Leaders will be downloadable cause the World Tournament says you can battle all of them from different regions. We also know that each Gym Leader can only use 3 Pokemon similar as to how the Battle Frontier usually works.
My question is what do you think the Gym Leaders will use? Some had more than three and obviously they'd use their best Pokemon. Though would they only use Pokemon from their Region?
I can see Brock sporting Onix, Golem, and Aerodactyl.
Misty I see sporting Starmie, Golduck, and Seadra.