re: The "future wildlife"
In reality, humans are unlikely to go extinct under any circumstances that would not kill off the rest of life of Earth, and if they somehow did, most future mammals and birds would probably be, as SDF alludes, descendants of dogs, cats, cows and chickens.
The reasoning should lead to a completely different conclusion:
Scorpions, insects will survive us and by far. Humans are much more fragile than those tiny beasts. Animals that have been bred by humans won't last very long without us.
Raoul.