It is too early to start working on projects listed here.
Implementing an infrastructure to run GIMP plugins on GEGL
The current way of accessing pixel data will be deprecated in GIMP 3.0, so it was suggested to implemnt an infrastructre to manipulate pixels with GIMP's existing API over GEGL. this will make porting plugins easier to GIMP 3.0.
Port UI code to a non-low level language
Category: User Interface, Future
Scripting line-by-line debugging support