I've been consistently negative about the prospects for metro WiFi. It's been doomed to failure from the start, usually championed by bored local-government IT drones looking for a new bandwagon to waste taxpayers money on.
There's a long list of negatives, but chief among them is that outdoor WiFi doesn't work indoors. It's useless. It's just wireless for traffic wardens.
So the demise of the Philadelphia poster-child network comes as little surprise to me.
I'm a little more open-minded about metro WiMAX (or maybe 3G), but I'm not holding my breath about that either, especially if it's at 3.5GHz - and 2.6GHz might be tricky too.