I think the next Pokemon game will be a Hoenn x Kalos crossover.  Both games have events that refer to a war 3,000 years ago.  A battle between Zygarde and Rayquaza.  And they are both green!  So I think it will be another sequel Pokemon game like Black and White 2, and would both emcompass both Kalos and Hoenn regions, just like what Generation 2 did, AND will have the Battle Frontier and Juan.