Should have a thread up on this topic by the end of the day.
There will be an opportunity to test a firmware giving you LibreELEC 7 (so Kodi 16.1 inside). It is in BETA stage still, so not official, not an OTA update, and I've not yet had a chance to test 4K performance, but once I've cleared out the threads awaiting a reply here, I'll get a new thread up. It will be in this area of the forum, and made "sticky" so should appear right towards the top of the first page.