Yeah and I think most of us are okay with them upgrading the UE. I just dont want them to throw everything out again and try and make a new in-house engine. Over the last decade quite a few Square projects suffered because they were building an in-house engine and games at the same time.Systems change and get updated. The old UE was creaking and very limited for what modern games attempt to create. The new ones offers a lot more flexibility, efficiency, and headroom for game design. It does everything the previous one does but does it a lot quicker and more easily. That's before you factor in graphical upgrades and new features and expanded scope. And with the seamless migration process It's not like they have to discard anything previously developed.
Sure some of the stuff they made won't successfully transition and need to be reprogrammed, but most things should be upgradable. Overall I think continuing with their current Kingdom Hearts adapted UE makes the most sense, seeing Unreal is making upgrading easier and they can keep a lot of work from previous projects.