I have no idea about Part 2(I mean why would I?). I'm sure the original plan was for it to be cross-gen. And why would'nt it? They said it would be a while before they went next gen only, the PS4 would still be viable until even 2022, and I doubt Japan is going to fully by into the PS5. And I think 2.5 years would be enough.
But the thing to remember is that while they will no doubt re-use assets and already have a lot of the systems in place. A VII Part 2 is still pretty much a new FF. It's not like XIII-2 or X-2. Those are budget conscious asset re-use sequels. They look "worse", don't have the same polish, or same level of production values as the previous game. I expect and would hope a VIIR-2 would be at the same level of VIIR Part 1. Maybe even better. So there's still a nice level of work. They have to meet the same standard of cutscene direction and animation, boss design and presentation, environment presentation(hopefully even better and more expansive), introduce more systems with new party members and so on. I don't think this project is like say .hack or Digital Devil Saga. Making pretty much one big jrpg and cutting it into parts. I feel like not having a trailer for the 2nd is kind of a testament. Part 2 to me seems like it will be actual sequel game in that I mean like Uncharted 2 from Uncharted 1. So when they say lots of things are undecided, fuck am I not surprised.
So I have no idea what they are going to do. Covid is going to mess things up. Next gen is going to be messy. I'm no tech person, so I don't know what they mean when they say you can just upgrade a UE4 game to 5. I'm sure it's more complicated then pushing a switch and now your UE4 game has UE5 stuff. Or maybe it is. I feel like having the game come out at the end of the gen puts it in an awkward position. But I think SE is clearly treating this as something bigger then a simple remake. So I think Part 2 comes out 2.5-3 years from now.
I just hope we also get a FFXVI in between.