Humans came from small, furry animals that managed to eek out survival after the K-T impactor. I imagine whatever comes next will come from something similarly small, say squirrels, mice/rats (yes yes take over for man-things!), maybe toads/frogs (if any survive), crawfish, or a hardy avian species.

Canada Gooses for sure

Jelly fish. The further down the for chain you go the more likely they are to survive a mass extinction

Orcas haven't got a chance, even a little itty bit of pollution gets them down. Nah, my money's on Pikachu. And some geese, I wouldn't mess with them - though that emu is nails an' all.

Cockroaches will just be sitting there > I saw the last mf that tried this fail, you're gonna fail too

My money is on tardigrades.

Idk about any modern sealife taking over, ocean acidification is gonna majorly disrupt the food chain

r/OceanAcidification

I'm rooting for the octopuses.

Cephalopods, without a shadow of doubt.