While some developers like DICE may have an early grasp of DirectX 12 thanks to already having worked with Mantle, I don't expect to see games utilizing hardware-level GPU features of DX12 for some time, at least until the next generation of GPUs (2016 on 14/16nm nodes). You may see some software DX12 support for better CPU utilization, but features like Conservative Rasterization and Rasterizer Ordered Views will likely go unused for a bit of time. Those features at the DX12 level will require levels of coding expertise beyond what is required now, so it will take some time for engines to be brought into line with the DX12 feature sets.
Now, I had heard there would be a D3D FL 11_3, which brought the advanced GPU features of D3D FL 12 or FL 12_1 to the D3D 11 API. However, does anyone know if features like CR and ROV will be part of 11_3? And, will it be easier for programmers to utilize those features or will they still be difficult to code for? I've heard the whole reason for 11_3 is to bring the visual benefits of 12 without the coding complexity, and without the reduced CPU overhead. I don't know if that means the visual features of 12_1 will be brought to 11_3 whereas the more efficiency-based features of 12_0 won't be brought over.