Here's a list of things currently in the works:
- Three more official maps plus a finished version of Skytop.
- A whole bunch of character options including an actual airplane costume.
- Custom voices for characters (including pew pew sounds).
- More models and brush types for map-making.
- Custom game modes that you define by placing certain objects in a map.
- Localization for languages.
- Map sharing with Steam Workshop.
- Macintosh version.
- A demo for Mac and Windows.
- Bots for offline play.
- Dedicated servers.