What Is The Announcement?
It has been reported by Serebii, who says that the summary of the upcoming episode states "there will be a major exlusive announcement within the episode".
The episode called "Guzma the Undefeated!" will air in Japan on the 1st September. This English version will not air until the 4th January 2020.
Its unknown what the announcement is or if it even relates to the Sword And Shield games, but for it to be a "major exclusive announcement" it must have a BIG impact on the Pokemon world and ultimately be reflected in the new Sword and Shield games.
Currently, the Pokemon anime is in its 22nd season called 'Sun and Moon Ultra Legends', which follows Ash's adventures in the Alola region,