GIMP is very feature-rich already and to me seems to be in the stage where change is more incremental.
The single feature that prevents my wife from moving from Mac/Photoshop to Linux/GIMP is the lack of adjustment layers. This is the ability to non-destructively modify brightness/contrast/colour/etc. In GIMP, if you edit the contrast, then edit in another way, there is no way to re-manipulate the contrast again without losing information. As per the summary, Krita does have this capability. Apperently it's in development for GIMP.