Lol, I don't think the new Ultimania is gonna do anything to move the needle on this "debate." The Ultimanias for the OG/Compilation have been explicit about Cloud/Tifa's feelings for decades at this point, and yet the "debate" rages on. Though I suppose hope springs eternal.
The thing is, you absolutely do not need an Ultimania to understand what is going on with the GS dates. Anyone with eyes, ears and access to YouTube can see that Cloud kisses only one person in all these dates and can pretty easily suss out what we're meant to take away from this. No need for a guide book for that.
The ending -- yes, parts of it are incomprehensible without the help of an Ultimania, but I also don't know if the Ultimania is going to clear up much since it's meant to be deliberately confusing/mysterious. There may be more hints, but this is a "mystery" that won't be resolved until we get part 3.
I am curious if they'll explicitly state or at least heavily hint whether or not the Aerith in the "dream date" scenario is the same as "our" Aerith. The more I think about it, the more her actions do not line up with the one we see in Ch. 13 or even the one praying at the altar at the end, who is so focused on stopping Sephiroth/saving the planet. (But given how inconsistent her writing has been throughout the game, I can't discount the possibility of her being the same.)
Regardless, I still find it a weird choice, since the game obviously wants us to think that this is "our" Aerith, but her actions left me feeling very conflicted about her character right up to her death, which undermines the emotional impact of that moment, especially since it also robs us of the full party's reaction.