Hard to say.......Star Ocean obviously has SE and it's an established IP, but it's coming out in a big month with SFIV and Yakuza 3 as well as close to the rumored PS3 price drop.
We haven't seen much of WKC and it's just 3 weeks away....And even though WKC is coming out with at a better time with less competition, I'm gonna say SO4 outsells it.