This sounds crazy but cephalopods are one of the closest if not the closest to developing intelligence and taking over the earth. Think about it:
> Use tools (coconuts, opening jars, etc)
> Can learn (pattern recognition, shape differentiation)
> Communicate with other members of their species, they are actually very social animals
> Can use delayed gratification, planning for the future

If humans die out they will be the ones to take over the earth. On top of this, they have dominion over 70% of earth instead of a mere 30% like humans. They will have the most vast powerful empires in history.

Reading:
https://en.wikipedia.org/wiki/Cephalopod_intelligence
https://www.msn.com/en-us/news/technology/cuttlefish-pass-marshmallow-delayed-gratification-test-indicating-intelligence/ar-BB1edsXO