I don’t think that would imply that nothing really matters, since reducing suffering and maximizing happiness (as well as good ol’ “care about other human beings while they live”) could still be valid sources of meaning. In fact, insuring that we do not become extinct too early would be extremely important to insure the best possible fate of the universe (that being a quick and painless destruction or whatever), so just doing what feels best at the moment probably would not be a great strategy for a True Believer in this hypothetical.
I don’t think that would imply that nothing really matters, since reducing suffering and maximizing happiness (as well as good ol’ “care about other human beings while they live”) could still be valid sources of meaning. In fact, insuring that we do not become extinct too early would be extremely important to insure the best possible fate of the universe (that being a quick and painless destruction or whatever), so just doing what feels best at the moment probably would not be a great strategy for a True Believer in this hypothetical.