It's coming by years end. Philly's problem is it wasn't launched as a digital market, as the others. Most of the other markets, North Texas, the Tampa area, Northern Jersey, and Pittsburgh, were all launched as half-digital, making the upgrade much easier. Philly must make the switchover to all digital before they add the new channels.
This is Comcast's big problem. Most of their systems are severely outdated, and are non-digital, or only partially digital. They need all-digital systems to add all the HD channels.