I think it would be majorly cooler to have right click "edit in gimp" and use Verse for realtime updates in inkscape. But since that hasn't caught on, I think we should push for integrating gegl rather than imagemagick. gegl might be able to offer us things like rendering for svg filters and such too.
I'd say edit in Gimp and suck in changes live (Verse or just file system) would be very good. Not trying to make Inkscape "do" bitmap manipulation is good, but so is making the workflow better.
If I can add my 2 bits as a graphic designer, I think this functionality would make Inkscape not only a Killer App (TM), but also part of a Killer Suite (TM).
I know there has always been talk of putting together a suite from Inkscape, Gimp and Scribus, but this might be a great start.
I agree that it would make the workflow better, and you wouldn't have to worry about trying to implement that which is already implemented in a much broader way in the Gimp - thus, there would be more bitmap-editing functionality.
One really cool thing about it, I think, would be the ability to edit embedded bitmaps without having to be concerned with separate files. That would save so much time and effort!