Interesting hypothetical, though I would put my money on birds rather than cephalopods :)
Octopi have impressive intelligence, but they are missing many other ingredients likely required for the rise of civilization: Intelligent bird species have them beat on complex social behavior, proto-language, long lifespans and security against predators. I'd say they are about tied on dexterity (parrots can do very nifty things with their claws and beak). And being able to fly is surely a massive boon for exploring and colonizing the Earth's surface. If the chimps didn't make it, I think birds would have the next-best shot at building a high civilization.
Octopi have impressive intelligence, but they are missing many other ingredients likely required for the rise of civilization: Intelligent bird species have them beat on complex social behavior, proto-language, long lifespans and security against predators. I'd say they are about tied on dexterity (parrots can do very nifty things with their claws and beak). And being able to fly is surely a massive boon for exploring and colonizing the Earth's surface. If the chimps didn't make it, I think birds would have the next-best shot at building a high civilization.