Can HIP run on AMD consumer Radeon cards? I'm trying to find the best option to write GPGPU code that runs on other people's machines with hardware I have no control over. I thought OpenCL would become the best way to write code that could run on all PCs and mobile phones, but from my research the GPGPU landscape looks more fragmented for each year.

Not officially supported... and no ROCm/HIP at all on Windows.

OpenCL is supported via ROCm on the new consumer GPUs now, so if the stars align HIP support might come too. The lack of announcements doesn't inspire much confidence though, especially compared to NVIDIA's always-on PR machine.

Is HIP continually evolving ala CUDA? For instance, every new version of CUDA seems to jam in new features to get things to launch faster, use less memory, be easier to use, etc.

It doesn't work on their new GPUs and many others. It's Linux only and etc.