No, CD Projekt weren't teasing The Witcher 4 - Geralt is coming to Soul Calibur VI

Update, March 15: Geralt will feature in Soul Calibur VI.

Geralt of Rivia will appear as a playable character in Soul Calibur VI. After several teases from CD Projekt Red staff and the official Witcher twitter account, the new character was announced this afternoon.

Imagine a Witcher 4 without Geralt. Well, don’t imagine it - read our article about why Ciri should lead the series from now on. 

The Witchergame twitter account tweeted to say “we are excited to announce that Geralt of Rivia will be joining the playable characters roster of Bandai Namco’s Soul Calibur VI.” That announcement includes a tweet from the Soul Calibur account, saying “A legendary warrior enters the stage of history. White Wolf, Butcher of Blaviken, the Witcher: he bears many names, but you know him best as Geralt of Rivia. Wield his steel and silver swords on the stage of Kaer Morhen, and use his signs wisely to take down all who defy you.”

from
https://www.pcgamesn.com/the-witcher-3-wild-hunt/witcher-3--geralt-soulcalibur-vi