we just posted 2012 TileMill + MapBox major investment priorities today: http://ds.io/mapbox-2012. In short, big push for:

- TileMill on Windows,

- Live map rendering for dynamic data via TileMill + direct uploads to MapBox for hosting,

- Beautiful new OpenStreetMap base maps as an alternative for Google Maps w/ its new usage fees,

- Shipping fast hardware (which we are still designing :) http://www.flickr.com/photos/developmentseed/5812414817/).