Cyno is speculated to be available in the game near future.
Cyno appeared in this Genshin official video.
You can see him in Genshin Offiial Manga as well.
Puzzles, Secrets, and Hidden Chests in Dragonspine
ATK% VS Physical/Elemental DMG% in Genshin
Puzzles, Secrets, and Hidden Chests in Liyue