It could be Yae Miko first, which would put her on February 16, or she could be the second banner, weeks later. But everything points to her being in the 2.5 patch, and as such, ...

Genshin Impact version 2.6 slightly adjusted Yae Miko's Elemental Skill, but the backlash by the community has compelled HoYoverse to rollback the fix.

Genshin Impact just posted the character teaser for Yae Miko ahead of her release in version 2.5. The teaser doesn't focus a lot on her playstyle but showcases her personality.