Why all the taxiway construction at PHL?
From the KPHL website


  Realign Taxiway H and Establish Taxiway EE (North)    
  
  This is the first phase of a multi-phased project to provide a 1,494
  linear-foot extension of Runway 9R-27L, construction of associated
  eastside taxiways and hold pads.  In this phase a new Taxiway EE will
  establish a connection between Taxiways H and K and Taxiway H will be
  realigned between Taxiway EE and the existing Taxiway D.
  
  Projected completion date: August 2016


As well as,


  9R-27L Extension - Site Prep, Utility, &amp; Fuel Line Relocation    
  
  This is the first phase of a multi-phased project to provide a 1,494
  linear-foot extension of Runway 9R-27L, construction of associated
  eastside taxiways and hold pads.  In this phase a new Taxiway EE will
  establish a connection between Taxiways H and K and Taxiway H will be
  realigned between Taxiway EE and the existing Taxiway D.
  
  Projected completion date: October 2016


The imagery predates the projected completion dates so it makes sense.