Persistent rumors of a pre-greenlit three seasons have followed Netflix's The Witcher series since its inception, but they've generally been just rumors and claims from industry insiders. Not so much anymore, as the show that had its second season confirmed before the first was released has now had its third season confirmed before the second season is released, if you follow me.
A posting on the Writer's Guild of America database was spotted by fan blog Redanian Intelligence. (Thanks, VG24/7.) That posting added "The Witcher Season 3 (2020-2021)" to executive-producer-writer-showrunner Lauren Hissrich's credits. The Writer's Guild of America is a very large union body, so it's pretty unlikely that they'd just make this up.
Season two of The Witcher is due to premier in the later half of 2021. It's unlikely that Season three will show up before summer 2022. You can find everything we know about that on the site.
Netflix has ramped up their investment in video game-centered series after the success of The Witcher's first season and Castlevania's three with a fourth coming. There's a lot of animation in the pipe: A CG Resident Evil series was recently confirmed, a Dragon's Dogma anime just came out, Splinter Cell is getting an Anime, a Cyberpunk 2077 cartoon called Edgerunners is coming, and even Cuphead is getting in on the action. There are also at least two live action productions in the offing, a Resident Evil show and Ryan Reynolds' theoretical Dragon's Lair movie.