The opensource implementation x265 of h.265 codec is impressive. File size is many times smaller than h.264. The following link contains a a free javascript library to show h.265 or x265 encoded video files: https://github.com/strukturag/libde265.js
When JWPlayer will integrate it?
I suppose the answer to your question is, "When browser support is reasonably widespread."
Remember, JW Player isn't actually "playing" the videos - it's just a steering script, passing the video to either the browser's native HTML5 abilities, or to a Flash plugin. JW Player doesn't provide its own codecs.
As MisterNeutron stated, JW Player does not have it’s own codec. We play videos in HTML5 or Flash that meet the media file specifications outlined here: http://support.jwplayer.com/customer/portal/articles/1403635-media-format-reference
Hope this helps! Let me know if you have any more questions
