It seems that some kind of announcement is coming tomorrow and it will be related to The Witcher series. The official Twitter account for the game has posted the following...
Now this is just my speculation but I think this is going to lead to confirmation that Geralt will be a playable character in Soul Calibur 6 as they have been teasing something for quite some time. Soul Calibur is no stranger to guest characters. In past games they have had Link from the Zelda series, Yoda and Darth Vader from Star Wars and Ezio Auditore from the Assassins Creed series.