As there is absolutely no mention of curses or ncurses at all in the source of any of the versions of sys-apps/coreutils currently in the tree, I think the dep can safely be removed as obsolete.
no idea when its usage (via termcap) fell out, but it seems to have left long ago ... so punt it i shall http://sources.gentoo.org/sys-apps/coreutils/coreutils-8.7.ebuild?r1=1.8&r2=1.9 http://sources.gentoo.org/sys-apps/coreutils/coreutils-8.8.ebuild?r1=1.1&r2=1.2