ESPN sportscaster Josh Elliott is poised to replace Juju Chang as newsreader on “Good Morning America,” sources said. Page Six first reported on nypost.com yesterday that Chang was moving to “Nightline” to be a special correspondent and fill-in anchor. We hear Elliott, who’s been filling in for Chang this week, is locked in to join the morning crew. For Chang, who has been contributing at ABC News for 23 years, it appears to be a demotion by newly minted ABC News President Ben Sherwood, who once worked at NBC below her husband, Neal Shapiro, then-president of NBC News. An ABC News rep refused to comment.