Well nVidia cards already support all 3 so you just pick one that best suits your needs so there is really no need to wrap anything and possibly lose something in translation.
Since OpenCL and DirectCompute are independent "standards" they should in theory operate the same on an AMD or nVidia card.
If you are talking about trying to take a CUDA application and have it run on ATI Radeon (STREAM / CloseToMetal) its unlikely to happen unless someone from AMD does it.