I just read on the PS Blog that they mentioned this. "Kat and Emmett will be available to download February 12th, and will be free for the first two weeks, so mark your calendar and get them as soon as possible! We’re not stopping there though. We still have some more All-Stars on the way, so keep your eyes peeled in March for more info!"
Waiting for: Ni no Kuni: Wrath of the White Witch PSN ID: Rammel29
Well, not to be a buzzkill, but actually, based on the specific wording they used there could be another interpretation...
"We still have some more All-Stars on the way, so keep your eyes peeled in March for more info!"
By using the upper-case "All-Stars" they could be referring generically to more content for the game (levels, horse armor, etc...). If they just said "more all-stars" then that would certainly mean characters.
I don't think they'd do that, but I'm just saying it's possible.