equery depgraph works with installed and non-installed package names, so completion should as well. I'll send really trivial patch in a moment.
Created attachment 214578 [details, diff] Patch for equery depgraph completion
Created attachment 214582 [details, diff] As above with indentation fix
Thanks, applied to trunk.
Thanks again for the patches. 20100613 is in the tree! + 13 Jun 2010; Jeremy Olexa <darkside@gentoo.org> + +gentoo-bashcomp-20100613.ebuild: + Version bump to fix bugs: 298919, 298916, 301582, 269498, 287092. Add + Gentoo Prefix support.