SNK let us know a while ago that KOFXIII would get a handful of new characters for the game's big HD console release. We know that two of these characters are Billy Kane, who has appeared in multiple past KOF games and Saiki, the final boss of XIII. A reported leak has revealed that only three more console exclusive characters will be released and there is also reason to believe that these yet unconfirmed characters will be sold as DLC and not included with your purchase of the game like both Billy Kane and Saiki are.
Unfortunately, if this thing is legit (and I'm obviously assuming it is), then that means that the unconfirmed characters are Iori with Flames (WTF), Mr. Karate and Shin Kyo. The image above says it much better though, as these 'new' characters (with Billy Kane being the only exception) are simply different versions of other characters who are already playable. Well, Capcom got away with this in SSFIV: Arcade Edition so I really can't say it's unprecedented.
Don't put any merit in this rumor until we get some official details. The King of Fighters XIII will be available on HD consoles on October 25th.