Improvements are made to graphics
Thats a huge understatement! God rays will be spectacular! With the in-development water reflection shaders and the already implemented bloom shader and shadows it will be very well modernized! I just hope my good old GTX 1080 will be able to output 60 FPS in 2K with ca. 400 nodes render distance.
I wonder if multi colored light will be addressed after 5.9, too.