It appears that the next character that will be revealed for Soul Calibur VI will be fan favorite Taki. Taki has been in every game in the series except for Soul Calibur V and well... the less said about that game the better. No official announcement has been made yet from Bandai Namco but this trailer looks pretty convincing.
Here is the trailer via Youtube user Wonkey. The trailer is low quality so I assume an HD version will be released in the coming days when the official announcement is made.