The official Pokemon Account already hinted at the content. It's Kalos DLC, or at least Zygarde.
https://twitter.com/Pokemon_cojp/status/1762130406239830297?s=20>いよいよ本日2月27日(火)はPokémon Day!>『ポケモン スカーレット・バイオレット ゼロの秘宝』のイラストを公開!>オーガポンとテラパゴスが見つめる向こうには何があるんだろう?>Pokémon Presentsは本日23時から!>お楽しみに!>Today, February 27th (Tuesday) is finally Pokémon Day!>Illustrations for “Pokemon Scarlet/Violet Zero’s Treasure” have been released!>What lies beyond Ogapon and Terrapagos' gaze?>Pokémon Presents starts today at 11pm!>looking forward to!The English tweet doesn't mention Ogerpon or Terapagos, and the image is clearly referencing Zygarde with the green hexagons in the shape of a tera star.
Johto and Unova both lost, Kalos won.