I tend to want to keep that secret to avoid creating any stressful situation for myself, you know like, too much expectations. Basically I work with Freerider when I have the time and inspiration, and primarily add stuff that I simply feel like at the moment.
New maps are always at the top of the list. Two of the other things that are on the top of my own wish-list is a very flexible map editor and multiplayer, but those two are also some of the hardest to make well so I'm not gonna make any promises about that at the moment.