I don't think Philly will get 2 shows. If NJ gets 2 as well, that will make 7 shows within a 2 hour drive of Philly in 10 months. If NJ gets one show, Philly could get two though.
We'll have to wait and see what happens, but on ZOO TV, U2 did 9 stadium shows within a 2 hour drive of Philadelphia in less than 1 month. They did 5 stadium shows on POPMART within a 2 hour drive of Philadelphia in 12 days.
Plus, New York City will have extra people coming from New England for the show. The show or shows in New York City will be the last U2 360 shows on North American soil which will naturally drive up demand.
Looking at Philadelphia, there are no shows south of Philadelphia until you get to Miami. While U2 have played these area's extensively already, its likely this leg will draw some people from these area's that are not getting a show. The Lincoln Financial Field is a smaller stadium than either the New Meadowlands Stadium, Giants Stadium, or Fedex Field.
If they can sellout the first New Meadowlands Stadium show and the first Lincoln Financial Field show, or at least come very close to selling both out, on the first day, then I think they will both get second shows.
I think they would first try to sellout two Philadelphia shows and one New Meadowlands Stadium show. Then, they will announce the the final show of the tour in North America as being a 2nd show at the New Meadowlands Stadium which should I think sellout or at least come close.