Nothing like that has been announced. The nearest thing that's been announced is that--as usual--we're not getting a Final Fantasy world.

Not me. I didn't even care about Final Fantasy when I first got into Kingdom Hearts (but I got to play a few Final Fantasies ever since).

It's new in that it's making its debut in KH3, but it's been Sora's Keyblade in a good portion of the KH3 advertising so far.

Granted while there has been no confirmed worlds from final fantasy, I'm sure they will add more final fantasy characters. In terms of new OC and FF characters per game, it's been as follows;

KH1:
5 new OC characters (Sora, Riku, Kairi, Ansem SoD, Kairi's grandma)
9 new FF characters (Squall, Cloud, Aerith, Yuffie, Cid, Tidus, Wakka, Selphie, Sephiroth)

KHCoM:
9 new OC characters (Axel, Marluxia, Ansem the Wise, Larxene, Zexion, Lexeaus, Vexen, Namine, Repliku)
0 new FF Characters

KHDays:
1 new OC character (Xion)
0 new FF characters

KHBBS:
6 new OC characters (Master Xehanort, Terra, Master Aqua, Ventus, Master Eraqus, Vanitas)
7 alternate OC characters (Braig, Even, Dilan, Aeleus, Ienzo, Isa, Lea)
1 new FF chracter (Zack)

KH2:
10 new KH characters (Xemnas, Xibar, Xaldin, Saix, Demyx, Luxord, Roxas, Hayner, Pence, Olette)
10 new FF characters (Seifer, Vivi, Raijin, Fujin, Setzer, Auron, Tifa, Yuna, Rikku, Payne)


Stands to reason they'll keep the new FF characters coming for the third Sora storyline installment. I'm guessing there will be a good amount of favorable characters from the franchise. Hopefully they'll still bring characters from the pre-FFX games.