Country Road ♪♪

A Noctis cameo would be pretty neat. If not that, either a Keyblade or secret boss  

I think a cameo of a few characters, maybe a keyblade or secret boss something is possible. It's hard to say what they will add, they are quite surprising at times

Something else. Nomura....

saves Stella from the realm of nothingness and puts her in KH3 as a recurring FF character in the series much like Leon and co. She has nothing better to do. Might as well.

 

Noctis cameo would probably be best

I read the thing wrong and thought of something like Noctis's ability to teleport, it might be cool if Riku could do something similar if he'd be playable again.

Most probably a Broody Mr. Noctis cameo! That's probably going to be the biggest kicker we'll get out of XV in Kingdom Hearts III! Just you wait, humans!

If Noct isn't in this game, it's going to be a huge missed opportunity. Same with Lightning. Or any main FF character from 6-backwards.

NOCTIS NOCTIS. Nomura is still salty about FF15 so he'll probably put Versus Noctis in rather than FF15 Noctis. The Sasuke Noctis. xDDD. It's not confirmed but it's got like a 90% chance of happening. 

A secret boss in the Keyblade Graveyard .

I want child Noctis in Twilight Town. He'd be a cool rival against Seipher (because Hayner doesn't do that rival job very well).

I want Noctis to have a role like the other final fantasy characters do in KH

I want to see Noctis as a cameo at the bare minimum.