Additionally, here's an example of how Caffe was porting using HIP [1]. To be honest, if the approach really does work, you might see a very quick increase in the number of applications ported.
All in all, given how elegant HIP is and that HCC seems to make GPUs more approachable than CUDA (and less silly than OpenACC), there is a great potential for AMD to gain some traction. My greatest concern is the quality and robustness of their software stack, their overly optimistic view (at least from the outside), and their relationship with the rest of the OSS world, especially given the conflicts that they seems to be running into with upstream contrib [2].
[1] https://www.youtube.com/watch?v=I7AfQ730Zwc [2] https://news.ycombinator.com/item?id=13136426