Phase one of the Crosstown is to be from Mt. Dennis Station to Kennedy Station. Phase two will extend it westerly to the YYZ airport.
Other line rail systems across the world (IE. Boston, San Francisco) make use of branches outside of the center of their cities. We could AF (after Ford) build a northeast branch of the Crosstown going north up Don Mills Road to Steeles Avenue East, and a northwest branch going north up Jane Street to Steeles Avenue West (or Pioneer Village Station), as phases three and/or four.
That would leave the DRL to serve areas south of Eglinton to the downtown, if the DRL study finds for using heavy rail.