Anyway, the story is moving in a somewhat more serious tone.
Shinobu isn't a fuccboi so if he goes all the way with Fumi, he will stay with Fumi. And Fumi, unlike previous side characters, isn't coming at him with anything but love.
Frankly, cockblocking Shinobu in the next chapter would so tone deaf that there would be a collective groan world wide.
Also, it would be very crude if the mangaka tried to bring the comedy back with Sakura trying to "save" Shinobu or any kind of role reversal. Even more if she tried the NTR bait with Fumi.
So more than likely the coming chapters will be Shinobu having the relationship with Fumi that once he wanted to have with Sakura. Sakura, having learned the truth and realizing that it was her that threw everything away will try to mend things with Shinobu only to be told that it's too late.
Shinobu and Fumi end together both with successful careers. And Sakura resets, with a new manager or something being her new "Shinobu."
I'm no mangaka, but something in this vein would certainly be very rushed, but it would make us all happy and it wouldn't leave her mainstream career in tatters.
This is the way.