If civilization ended and cannibalism became the only way to survive, I can imagine that an Epicurean would sacrifice themselves or give themselves up for another's food because at that point "the party is over" meaning that a joyful life wouldn't be possible anymore, and it would also be chosen since "death is nothing to us".
I agree with that, but with the critical caveat that the issue would not turn so much on "civilization" but on those who are our family and "friends" (which would be an interesting issue to tackle as to who fits that). In other words there are people whose existence are critical to us, and people who we have essentially no relationship to, so it would be important to make that distinction. But in the sense of "the world of living human beings" for example if the entire earth were being destroyed by a meteor there wouldn't be much to argue about