For me, this is the biggest problem: so many things happen off-screen, leaving so much to our imagination, all because of those stupid time jumps. I also think that after her conversation with Fumi, Sakura must have felt guilty and sought out Shinobu, and they resolved things, but they wouldn't have ended up as a couple.
A 5 year time skip will do that. Hard to say definitively on whether they reconnected as a couple (probably eventually if not yet), but working together again is a good start and Sakura was walking around wearing the necklace before any of this, while Shinobu looked happy at the chance to work with her again.
While the use of time skips was excessive, and the ending poorly paced, ultimately it's because of them breaking apart that Shinobu ended up becoming a successful director. As her manager/boyfriend he was reaching the limits of what he could do for Sakura as she continued to grow.
My opinion is that if Keishi is in charge of the extra chapter, she'll show us Shinobu and Sakura's reunion and how they resolve things, including having a lot of sex. Sakura will demonstrate that she genuinely enjoys it and realizes how different it is from when she slept with that fuckboy. This will show that she truly loves Shinobu and lessen her hatred towards her. But if Katsura is in charge, she'll probably write chapter 129.5 or another chapter about chico
Well a reunion would be more than enough for some because the ending really didn't give us any real ShiKura interactions other than "look they're working together again and still have feelings for each other". As for the tons of seggs part its a 50/50 since seggs scenes are notoriously tedious to draw but since it is the final volume there's maybe a chance but I'd just take it as a bonus if it's there (inb4 ChicoXRyusei).
Sakura walking around with the necklace after 5 whole years is all that's needed for where her feeling are at in present, which makes it all the more dumb how things were written out because not enough time was left to show the important things.
The hate for Sakura didn't die down much. Fucboi disappearing, and her finding out the truth plus reconnecting with Shinobu do help a bit, but the lack of a proper ShiKura interaction hurts that idea, and Sakura's weak ahh 1 panel death stare reaction to the truth bomb isn't much of a payoff for the months of waiting.
If it is a 129.5 it really would feel like Katsura putting up the middle finger as she exits stage left, a very low chance, but it will have a positive impact on sales imo, maybe even more than a wholesome bonus who knows.