In 2013 we started GPU programming at the company I work for. We carefully evaluated CUDA and OpenCL and decided to go for OpenCL because it was a standard and we could chose between 2 vendors of GPU. I can tell you that in 2017 we do not regret our choice. It is great to be able to run our code on both AMD and NVidia GPUs, and to offer our customers to choose whichever GPU vendor they prefer.

Many people criticise OpenCL because when you come from C++ it seems a lot of work. It is true that OpenCL has an API influenced by OpenGL and is verbose. However it is not difficult to write a small framework specific to your needs and domain to factorise much of this verbosity.

NVidia does everything it can to hide the fact that their devices support OpenCL. People thinks that only ancients versions of OpenCL run on NVidia devices. That is not true: 1.2 is not ancient is still as of today the main version of OpenCL used. OpenCL 1.2 is fully supported and NVidia quietly say to its large customers who refuse to use CUDA, that they will starting to support soon some OpenCL 2.0 features.

To answer your question, I am not sure either will win, but they will both exist for a long time.