It's always nice to see leaks like this. They bring a little slice of awesome, a chance for a developer to see a reaction to a feature early in development – even if the feature turns out to be non-existant, as is occasionally the case. Of course, that means you've got to take them with a pinch of salt, and this is by no means an exception.
Sent to Joystiq via an anonymous tipster, this photograph of Soul Calibur 5 clearly shows Ezio Auditore, hero of Assassin's Creed 2 onwards, as a playable character.
It's certainly not out of the realm of reality, Soul Calibur is well know for having guest characters – who can forget playing as Link or Yoda?
Either way, its not official quite yet, so enjoy it soberly until it comes from a better source.