darkSpyro

Theory 1: Pokemon Z & Delta Emerald

2 Games were you go to BOTH Kalos and Hoenn...

Theory 2: Pokemon: Dirty Yellow or Pokemon: Brown

Bidoof is the Plump-Mouse, and Pikachu is the Mouse...
And naturally a Sinnoh/Kanto remake is necessary.

Thoery 3: Pokemon Brown

Remember that interview with the keyword, 'flowers'? Take a look...

1. Take the word 'flowers' and it has a 'w' in it. Being a 'Double u'. So we have 'flouuers'
   
2. Next, turn the second 'u' 180° and it becomes 'n'. So we have 'founers'
   
3. So we know its a key word, take the 'd' and move it after the 'n'. So we have 'flounders'
   
4. Have a look at all the Pokemon. Do we have a flounder? Yes. Stunfisk.
   
5. Pokemon Brown: Stunfisk Edition CONFORMED
   

I think Z will take place in a region behind Frost Cavern's mountain, which geologically is Germany. I based this off that the hiker who gives you the Strange Souvenir denies claims of it being any previous region, and it's a hiker. Since Z will focus on Zygarde, and it's dex entry says it awakens and reveals it's "secret power" when the ecosystem falls into disarray, I believe that the game will take place one year after Kalos has fallen, with people moving to the Germany region, and the professor there asks you to go on your journey beating the 8 gyms, elite four, and you go to Kalos to finish the main story, calming down Zygarde, taming it (catching) and restoring Kalos. There would be 4 returning Kalos leaders and 4 new ones.