Some sort of bike sharing program will arrive in the urban hellhole at some point if the stars align correctly. Philly's a good biking city. It's flat. Most streets are one way (pay attention, bike salmon). Outside of central center city, roughly Market St. to Pine, the busiest bits of West Philly, and a couple of additional mostly avoidable thoroughfares, there really isn't all that much traffic.
Having said that, I'm personally a bit fearful of urban biking, but I'd use it sometimes if they put some bikes near me.