Joystiq has just received a photo from an 'anonymous tipster', claiming that Ezio Auditore de Firenze from Assassin's Creed is featured in Namco Bandai's upcoming Soul Calibur 5.
If you click through the link, you'll see a photograph, taken at a recent tournament, where a Beta version of Soul Calibur V was being shown.
We're inclined to believe the rumour. Far, far stranger things have happened in the series, which has become known for its guest fighters. Both Yoda and Darth Vader featured in Soul Calibur IV, and I remember Link being incredibly overpowered in the Gamecube version of Soul Calibur II.
We've reached out to Ubisoft for confirmation and will update if we hear anything further.