"In a strict reading of quantum mechanics, the cat is neither alive nor dead at this stage; it exists in a quantum superposition of both alive and dead. Only when we open the box will we know for sure, and it's also the act of opening the box that allows that superposition to collapse and the cat to (suddenly) exist in one state or the other."
Our CERTAINTY about the cat's survival is open. But, that doesn't make the cat both dead & alive.
Put enough food & water in the box. Don't open the box. If after a week it stinks, the cat is dead. It isn't dead 'suddenly' because of anything we do.
It seems ego- (homo-) centric to think that everything happens because of our actions. When I die, things will keep happening -- clearly; some cats will die, some will not, without my opening anything. Let humans become extinct. The remaining cats will live or die. We who have shuffled off this mortal coil may not know it. But our failure to open the cat's box has nothing to do with its survival.