While this will be fluid, based on community needs, here is the initial Astrogeology software roadmap for FY19 (and into FY20). https://github.com/USGS-Astrogeology/ISIS3/wiki/FY19-Roadmap
While this of course covers our ISIS3 image processing system, we now include other efforts like the Community Sensor Model environment/toolchain, plio (data I/O), PyHAT (spectral env.), and AutoCNet (matching env). Of course, we will continue to actively support GDAL efforts also.
As stated on the wiki, we are focusing heavily on addressing technical debt, engaging our user base, and making external development more viable. Ideas and code contributions for these projects are welcome. Please use this forum, Astrodiscuss, or Github to discuss your ideas or needs.