Well since you didn't provide any further info about the animation you were talking about, I took an initiative and found it myself. After taking deeper insight into it (especially after I've watched recordings of your presentation from Guadec about ZeMarmot) I've understood why you are so interested into it and also meaning of animation in GIMP. I'm still firm about my words that it would be better to make animation support via plugin rather than hardwire it into GIMP, but I think we are on the same line about this one.