Bad news, the inklings are on a different evolutionary line. The octopus pass us up.

Oh dang, this just started as a joke, but now I have ideas...

We eventually twist the climate so badly, a massive flood all but eliminates mankind (Thus making the 1995 movie Waterworld canon.) The octopus have a field day in the exciting cities we have built that are now underwater. They explore our tools and machines, and they begin to learn and grow. Millions of years pass, and the Earth starts to reset. Although it has changed immensely, the oceans recede and ancient cities rise from the water. The octopus are forced to follow the water or adapt, and eventually those that stayed on land take over and build onto the cities that we had left behind. Inkling society begins it's reign.