the only villain on staff
I think he is hinting at two things at the same time: a new worldline and also a new line of something.If by "line" he means "worldline" , I believe the third one is where we will have TWEWY and Verum Rex.
1º worldline: The age of fairy tales - KHX stuff (Past)
2º worldline: The main one we've been playing with Sora and co. (Present)
3º worldline: "The real world setting" TWEWY, Verum Rex... (Future)
We have KH the series and then [chi] the mobile/browser series, and now a third one that is both a new worldline within the multiverse of KH and also in its own format—A novel, TV show, shorts, or what have you.