I'm making steady progress on the new 1.17 version of the mod. I've gotten the new object registration code pieces worked out, and I'm working on those magical horse models.
For now I've commented out some of what used to be called "Tile Entities" but are now "Block Entities." This includes things like the Oracle and Tree Holes. Depending on how hard those are to change over, I may put them out after I get the main feature (the magical horses) done.
After looking deeper at the official Forge migration guide, it seems like there are some pretty cool new things going on under the hood, like some new rendering capabilities, new graphical user interface options, and new a complete fluid overhaul. I don't know how I'll make use of any of these new capabilities, but there could be some fun opportunities there.
One of the things I look forward to after getting this done is updating the horse speech interface. Right now in 1.16.5 it works fine, but there really should be some extra bells and whistles, like actual inventory-style trading boxes and such.
Anyway, I'll keep on working, and hopefully I can get this new version out soon!
Thanks for your patience!