Ruliweb managed to get hold of news and some screens that seem to indicate that Soul Calibur 3 is set to make its way to the PSP. The report says that Soul Calibur 3 will remain largely unchanged from its PS2 version. Above is a screenshot seen on Ruliweb.
What makes this rumor a bit shaky is that it is quite difficult to confirm the information. As noted by the folks of PSP-vault, the screenshots featured by Ruliweb has watermarks of Famitsu.com, unfortunately they were unable to find a corresponding article on the Japanese news site.
Moreover, as of this writing it seems that the Ruliweb article is no longer up. Pulled out perhaps due to people spotting a fake, or perhaps because of a request from Namco Bandai? Regardless, it seems that the promise of getting to play Soul Calibur 3 on the PSP is welcome enough to warrant this much speculation.