Our mapping framework is rather flexible and terrain maps with off-road navigation are definitely on our to-do list (one of my colleagues drives a Range Rover). We do not plan using any particular map format directly, instead we would like to provide format description so people could write applications or scripts to import their particular format. We might create importer for the most common formats in-house, but this is all relatively low priority and will most likely be done in Q3 this year. The on-road navigation is the top item now - it works, but there are still a few glitches (i.e. route finding is relatively slow for long distances etc.)
APRS is one of the things in the pipeline - my colleague is currently looking for a suitable transceiver that he could install and control via QCar. APRS is something he would like to do as well.