They probably won't "roundhouse kick" it, because it's still needed for backwards compatibility with older versions of D3D (including the lower Feature Levels in D3D12).
Debug/Release has nothing to do with this. They both support the Debug layer. The reference driver is probably also what they send to hardware manufacturers as example of driver implementations... The WARP driver is simply an implementation of the reference driver optimized to use SIMD/SSE, and I think it's used with Store apps when there is no hardware acceleration available.
In fact, MSDN has this to say:
Because WARP uses the same software interface to Direct3D as the reference rasterizer does, any Direct3D 10 or 10.1 application that can support running with the reference rasterizer can be tested by using WARP. To use WARP, rename D3d10warp.dll to D3d10ref.dll and place it in the same folder as the sample or application. Next, when you switch to ref, you will see WARP rendering.
But the only good reason they can't drop the reference rasterizer is probably ( ) because officially Microsoft only requires that SSE is supported by the CPU for 64-bit versions of Windows. The 32-bit Widnows can still be installed on machines without SSE (or even MMX?), and there the WARP driver cannot be used.
Of course, we can all just take a look at (and test) D3D12CreateDevice to see what it supports.