Obviously there has been lots of talk about what will be replacing zombies. But I think this is the wrong question to jump to.
The question should be - What happened to this world? This will then give you the answer to what should replace zombies.
Here are a couple of scenarios I came up with, would be glad to hear others.
After World War 3 -“I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones.” - Albert Einstein. All out nuclear war. Mutants (animals and people) and Military.
Dimension rift/rip - Similar to Half life or “The Mist” / “Pacific Rim”(without giant robots) movies. Various monsters
Alien Attack - Aliens come down, reduce us to ashes to ensure we do not pose a future threat. Alien type creatures left behind to manage uprising. “Avatar” movie monsters, plus some with better tech.
10,000 AD - Don’t know what happened to civilisation, but animals have evolved (like After Earth -although I didn’t actually see it)
I don’t think we need a Skyrim FPSMMO. Happy for flying creatures, but don’t need Dragons. Would like to see big cats (sabretooths).