Development on 4.0 has stalled due to working on Avalon and Traq at the same time and with reduced time to work on Traq it would be better to switch to an already established framework such as Symfony or Laravel.
This would increase the development speed of 4.0 and future versions.
Likely candidates are:
Development on Traq 4.0 has been restarted, the chosen framework is Laravel.