For now, the only hardware that has this decoder support is the GTX 960. It’s likely that upcoming mid-range cards will support it too (950 and 950Ti have been leaked). It is normal practice for nvidia to refresh the video decoder block ‘mid-cycle’ - it shows up in the mid range versions of a given chip family, with the early high-end parts keeping the previous generation decoder block.
I implemented support for VDPAU HEVC in ffmpeg last month, but it’s currently useless due to a driver bug which means that decoded frames are messed up. This has been fixed internally by nvidia but it’ll be a while before a new driver release shows up with the fix in it.
In terms of when support will show up in Kodi? Well, first the updated driver needs to ship, then we remove the experimental flag from the ffmpeg code, then an official ffmpeg release needs to go out for Kodi to target, then Kodi may need some explicit code to use the hevc decoder, but it might not - depends on how it’s written. If explicit support is required, it may show up in a 15.x release, or may be left until 16.0. I actually think it’s likely to be 16.0 because the ffmpeg release will be 2.8 and I think Kodi will stick to targetting 2.7.x for the 15.x lifetime.