I don't know whether this has been mentioned or anything, but I was reading that Kuja and Jecht appear to be on the Cosmos side, which is apparently indicated from the box art. Which would mean IX and X are left without characters on the Chaos side. So what will happen here? Will they have villains from these games?

I'm hoping they do and add in Seymour and either Necron or Zorn and Thorn. But it's not official that Kuja and Jecht are Cosmos because I read it on the FF wikia page.