GIMP is a handy tool: I use it for a lot of my image editing needs, for when very basic tools won't do. I rarely need the power of PS, and can't afford it anyway (although I do miss that magnetic lasso: GIMP's magic scissors don't quite have a good enough algorithm). All of this talk about the future is exciting.
However, yes, GIMP is quite rarely an acceptable replacement for PS, and I find this unlikely to change any time soon.
Also, GAP is really, REALLY, REALLY awkward and unwieldy to use. I would reccomend Synfig Studio for animation instead.
GIMP's new (though not actually young) engine - GEGL, contains ffmpeg frame sources and sinks, provides a good abstraction for creating interfaces better than GAP for animation or video editing - see https://www.youtube.com/watch?v=GJJPgLGrSgc for an example of a video that has been edited and encoded using GEGL this year.
Synfig focuses on more cartoon based vector animation. What GEGL provides good foundations for doing is video editing/compositing with keyframed properties for filters.
As mentioned in the linked article of this story - having an eco system of applications using GEGL would benefit both these applications and GIMP - since they would be sharing image processing operations and plugins.
However, yes, GIMP is quite rarely an acceptable replacement for PS, and I find this unlikely to change any time soon.
Also, GAP is really, REALLY, REALLY awkward and unwieldy to use. I would reccomend Synfig Studio for animation instead.