Although it is true that since the last release (4.3.0a) that 20 months have passed, it would be incorrect to assume that there is a lack of development activities.
The intended version (4.4.0) was not released last year because of quality issues.
A major goal of that version was to support the ISO/IEC 13249-3 Topology standard, based on the rt-topo library.
Extensive quality tests from outside sources showed, that a release at that point could not be made.
So most of the development work until about March was in this direction.
At present a Spatialite 4.5.0 is being prepared, a full description of which can be found here:
current state of the art and 2017 roadmap:
This was a portion of the (then called) 'RasterLite' portion of the Spatialite project.
It has been completely replaced with 'RasterLite2', which is now in its final stage of development:
These summaries should assist you on your research for your supervisor.
Mark