In the latest update, 1.5.7, I put in a feature that I've been wanting to include for a while: New custom unicorns are downloaded by the mod automatically when they are created, instead of requiring a new release. This feature lets people get their custom unicorns quicker, and makes it so I don't need to put out a release every time I get a new order.
Looking forward, I definitely want to include new horse breeds, and at some point I will likely put up another poll to see what people want (although I already have an idea what the favorite(s) will be).
I'm also thinking in other directions. Of course, a boss would be cool. A new dimension would also be cool. There are two ideas that really grab me, though, but both are a lot of work:
Idea 1: Multiplayer Games
Multiplayer games could be really fun. You can already see some of my efforts in this direction with the lance items, and how you can use them to joust. I'd like to create a mini-game in which players are positioned in the jousting lane and points are awarded for unhorsing your opponent. Such a thing (as well as other types of mini-games) could lead to some fun competition on a dedicated server.
Idea 2: Quests
I like games with stories, and I like to tell stories. Adding in a series of quests would be a great way for me to do this. Some of the basics are already in place, including the Oracle, and some underlying code that will let you talk to magical horses and other non-player characters.
Anyway, just throwing some ideas out there. The last few months I've been pretty busy with other parts of my life, but I'd like to get some new and interesting features into the mod now that things are returning to normal.