This makes no sense whatsoever - there is never “everyone is doing it” with game engines - they all develop individually and focus on different aspects in order to be competitive with one another.
IO Interactive use a bespoke engine and quite possibly have their own metahuman creator along with many other considerations to take into account like rigging configurations, cloth effects, etc.
Saying this is the future for IO Interactive is like posting a picture of Mercedes Benz and saying it’s the future for Porsche. One thing has nothing to do with the other.
The main excitement over the Metahuman creator is that it means all the studios who use Unreal 4 are now going to be able to produce figures, so smaller scale shops will be able to put more actors and a wider variety of actors in their games because they won’t have to spend fortunes on 3D modelling them. It’s very exciting to people who are wanting to see more diversity and better depictions of different kinds of people in games.
Big shops will still be doing it their own way because they have custom considerations - lots of the smaller shops will too.
It’s complicated and it helps no one to just post “I found a thing on the Internet and assume it applies to everything”