personally i would rather developer to put their focus on developing their games first and fix any stability issues before venture into more complicated things like low level API. even with mantle where Dice only have to deal with AMD hardware it is not that smooth sailing for them. if Dice want to support Vulkan then there is no reason for them to use DX12 at all. because Vulkan pretty much able to do what DX12 can and have no OS restriction. since they already support DX12 it is very unlikely for them to support Vulkan.