I don't see North Philadelphia being turned into "the" stop for Philly for any longer-distance trains barring a major station rebuild/expansion. As I understand it, the station is a very "functional" commuter station with very little Amtrak traffic; if you want to have the Pennsylvanian, Three Rivers/Broadway, or anything else major only stop there, you're going to have to do something to allow for connectivity with trains such as the Silvers, Crescent, and the Regionals (among others)...and you're going to need a moderate-sized waiting area meant to have folks waiting for a few hours for those connections (i.e. probably containing a coffee/snack concession that is open all day). Also, the station would likely need a boost to parking as well.