Different surfaces aren't planned since the physics wouldn't really work well.
Banked track pieces will most likely come next update!
I have no plans to stop working on this game as long as it remains popular and people keep playing it.
The community seemed to be mostly against controller support in the past, since people worry it will give players using controllers an unfair advantage.
It might be possible to have separate leaderboards for keyboard/controller, but it'll be quite easy to cheat and submit a controller run to the keyboard leaderboard.
There is also a small modding community in the Discord!
Different times of day and environments will come at some point! Not sure when though.
Boosters might come in 0.6.0 or 0.7.0, but nothing is decided yet.
Being able to select a start position when testing the track in the editor is planned, but it's quite low priority for now.
Trees and other decorations is something I want to look into for the next update!