Though a release date is not yet set, Deus Ex: Mankind Divided seems to be shaping up well. With a release in 2016 'somewhere' it will get DX12 support straight of of the box (well, digital download). That's as well as an internal benchmark.
AMD's Chief Gaming Scientist Richard Huddy talked about having their technology and support in Deus Ex: Mankind Divided. Since they used Mankind Divided in their own internal materials.
Huddy confirmed saying that Deus Ex: Mankind Divided would indeed launch with DX12 support. Mankind Divided will also include AMD's own TressFX Hair 3.0 technology alongside DX12. Huddy confirmed that Mankind Divided will include a built-in benchmark, too.
Update: current release date is 23.02.16