Its no surprise to see Soul Calibur to have any guest from another game to be playable for each sequel. This time it may be possible to have our friend from Assassin’s Creed: Ezio Auditore da Firenze, be Soul Calibur 5’s guest character.
“Unfortunately, we don’t have confirmation just yet, and there’s no information about whether Ezio is limited to a certain version of the game, or available to anyone playing it. But one thing is for sure: The Hidden Blade would look pretty nice decked out with Soul Edge finery.” -Joystiq.com
With Ezio’s sweet moves from Assassin’s Creed 2 & Brotherhood, I think Ezio would make a good addition to Soul Calibur, not to mention his attire also makes him fit into the Soul Calibur universe much more than Yoda & Darth Vader.