CoroCoro's teasing some Pokémon news set to be revealed on December 15th. On a page in the popular Japanese gaming publication's November issue, the magazine discusses what they've got in store for their December issue, and part of that is a message teasing something apparently big and Pokémon-related that'll be hitting us in 2016.
It's uncertain exactly what that news is going to be about, but Pokémon website Serebii claims it might very well be regarding the next Pokémon movie, as CoroCoro often reveals details of the next upcoming Pokémon movie in its December issues. However, the magazine itself doesn't say anything to specifically, so we'll have to leave it up to speculation until December 15th.
Source: CoroCoro (via Serebii)