As far as we know, he’s about halfway done, probably around 60% by now, maybe even more. You can check r/eternumites on Reddit for updates, people often repost progress info from his Patreon there. The latest post about the progress, as far as I know and as I mentioned below, is here :
https://www.reddit.com/r/eternumites/comments/1lk8ozy/eternum_v09_status_update/...