The comment you linked talked about reliably predicting future experiences, and I'll reliably not be experiencing a universe after my death -- so doesn't that mean that the universe won't exist if I shared your definition of "exist"?

I don't see why. A half-decent model would not center on a single person, and the definition given does not say that "future experiences" are those of a specific person. Unless, of course, the model in question strives to describe this person's sensory experience, in which case, yes, you likely stop sensing the universe after you are gone.