This might be a hated response, but I’ll lay it out anyway.
Cheaters are forgiven all the time. There are plenty of marriages and relationships that go through infidelity, and the people involved still end up back together. That does not mean everyone has to agree with it, but it does happen.
I think Shinobu is going to fight hard to at least talk with Sakura. Whether he is successful or not is a different question. If they do get the chance to talk it out, then there are really only two paths forward: they either end things completely, which happens all the time, or they try to work through it and rebuild the relationship.
Unfortunately, Shinobu was protecting Sakura from her own weaknesses for a long time. But Sakura is an adult. If she walks a path without Shinobu, then she is going to have to grow on her own and take responsibility for herself.
I honestly think Shinobu is strong enough to move on either way, but it would still be heartbreaking at first. Anyone in his position would struggle with that.
I think a lot of people view Sakura like she is still a child, but she is an adult. At some point, she has to grow up and take responsibility for her life and her actions. The safety net will be gone and that is her decision.