Sure, but it's still the hopeful that existed at the end of Mad Max Fury Road -- Immortan Joe is defeated, there's water (for now) and some food, and people aren't under the yoke of an oppressive ruler for the moment. That's hope, sure, but not of saving the world. Defeating the Sorcerer Kings, likewise, was more of a power trip than saving the world -- the world is still dead, the Sorcerer Kings aren't what's keeping it dead (though they don't help), so defeating them doesn't really lead to saving the world -- just like defeating Immortan Joe and his brothers didn't lead to the saving of the world. But, yeah, local hope is worthwhile. Saving Athas is beyond the scope of the materials, if, as always, within the scope of your table.