Here's another unexpected event! You can get a Shiny Xerneas in Legends Z-A with the code:
CELEBRATE30TH
It runs until January 7, but you probably want to get this one right away since it's a shiny. I don't know if this is the only one they're going to do, or if we'll also get Shiny Yveltal and Zygarde before the year's over.
They are calling this current online battle season Ranked Battle Season "X", which you would think would be a cute way to call it Season 10. But, they reached Rank Battle Season 19 right before this in October, so this is just a special name they're calling this season. So, we could get a "Season Y" and "Season Z" to celebrate the 3 different types of Mega Stones in the game.