I noticed yesterday driving in the area that the proposed Northern Parkway is under construction. It's supposed to go from Loop 303 to Grand Ave, using the current Northern Avenue alignment and move up to a half mile north of Northern at its west end. It's a Maricopa County project, with contributions from the cities of El Mirage, Glendale, and Peoria. When completed (sometime in 2015 or later) it will be a major east-west route between I-10 and Bell Road.
Map of project: http://www.azcentral.com/ic/community/northernmap1024.pdf