Qt based apps must be under development now. 4.6 was just out and 4.7 is bringing a lot to table. So, getting it out based on Qt will not happen now. There are some differences between M5 and M6 UI and they need different UI code even if they code it in Qt. Also, turn-by-turn navigation needs text to speech converter. This is still not available on Maemo from Nokia. So, there is a lot which needs development and my guess is Nokia is in fix. if they spend time on M5, they will get delayed on M6.