I mean, this is exactly what they wanted. They wanted fans to have something to talk about, to theorise about. Look at people, elaborating theories, posting on twitch, YT, reddit, their theories, informing themselves, playing the OG and other games - the devs have won. They have made the first part of Remake super interesting because no one can truly answer as to what's coming. Old fans are lost. New fans are lost. And a lot of people, really a loooooooot of people, absolutely love this, old fans and new fans alike. Yes, they don't understand the ending, but they do love this feelings of being in a lively fandom.
If the devs had made Remake just a pretty version of the OG, would it be as interesting? I don't think so. I think people absolutely love to theorise - look at A Song of Ice and Fire, hell even Harry Potter back in the days, look at various series such as Lost, X-Files, etc. Why is/was the fandom alive? Because people love(d) to confront ideas, see if they could find something that made sense out of it and if they were right. If it was just a retell, it would be boring, we would know everything. But it's more than a retell.
However, Kitase has already stated that the OG plot would remain - the backbone of it will be there. To me, what it looks like is:
- retelling of the OG while encompassing the whole Compilation so that everything fits neatly
- expand on ideas they could not expand on in the OG
- expand on characters and background (I'd appreciate that the characters' stories remain impactful during the whole journey... a lot seem a bit lost in the overall plot aside from Cloud, Aerith and Tifa)
- expand on zones, quests
- possibly put a final nail on Sephiroth
So will there be a lot of differences with the OG? Well, yes. Because they expand on things, because the first game was already different from the OG, I think that the next games are going to be different, and at the same time, the backbone of the OG will still be here. That's my take on seemingly contradictory statements from the devs, yet I don't think that both can't be right at the same time. Look at Remake, and think about what Nojima stated - that it was going to be different because of the game's realism. They are going to fill in the wholes our own vivid imagination filled, back then. Even the interactions are somehow different. Anyway it's getting late and I'm rambling already, sorry. But you get the idea.