FucboiXSakura: Fucboi is unable to accept Sakura's career decisions in the end despite blonde's advice due to his possessive and narcissistic nature. Sakura runs into agency issues with her "image" shifting and transfers to Mio's agency.
ShiFumi: Shinobu decides to keep filming the scene, the two get into an awkward spat but push on to finish the filming. With the movie done ShiFumi don't have much reason to be around and eventually drift apart.
Of these two, the least likely to break apart imo is actually ShiFumi. Fucboi X Sakura, it is harder to gauge because the interactions that we are shown between the two have been much more specific and limited compared to ShiFumi (the 134 convo) so that we don't get a real sense of how their relationship truly is, especially in the post major time skip (still 0 romantic interactions on screen). Conversely while we have seen much more organic and romantic interactions with ShiFumi, a bit of a bomb has now been dropped with the 135 cliffhanger, which is not a nuke per say, but will have many people freaking out because it is KA behind the wheel.
All this is to say, KA is being very inconsistent here with how ShiFumi is being treated, that even though fucboiXSakura may have not been shown as much, there IS the chance their relationship ends up being the stable one, even if it goes against the fans wishes as these two are clearly the most hated characters right now still imo.