Maybe Nomura just needs a damn break for once, also to get a hold of himself about the whole XV-saltmine.
Depending on where the FF 7 remake stands development wise there might simply be not much room to squeeze in new KH stuff beyond the KH III DLC right away.
This is what I think is really going on. The man's schedule is so jam-packed, and KH3 released at the end of January, we're just about to hit March. It's also pretty clear that from here on, his focus is going to be on FF7's remake and whatever else that takes priority.
He's been working on Kingdom Hearts non-stop, so he's probably just burnt out. Add to the fact that both the remake and KH3 are titles with a huge amount of pressure that come with it, I could see why he'd say something like "if". To me, KH3 delivered on what I wanted, might not be a perfect masterpiece, but it didn't need to be. So, I'm okay with waiting for a bit now, I'm full-speed ahead for the FF7 Remake. The paid DLC should be enough to tide me over.
Also, I realize that this is a hot take, but I actually loved the XV/Versus stuff in KH3. I personally don't mind the salt, but I can see why many wouldn't like it. If he can reuse ideas from a game that never got to see the light of day (HIS version, at least), and make it work, I'm all for it. May as well not let it go to waste, if he feels this passionate about it.