I really doubt they are so interested to promote Koraidon and Miraidon at this point. I mean, the games have been released months ago.Finally we will find out what is up with the random shiny Rayquaza... But why should we care about the Gen 3 legendary in a series that should be promoting Koraidon and Miraidon? What was the point of their cameo in the TR specials if they won't be relevant in the new anime?
Not to mention that previous seasons of Pokemon doesn't focus so much on the legendaries either.