In mid-April we reported that due to constraints of replacement units for the discontinued white 16GB GSM iPhone 4, Apple Store Genius Bars were told to swap out these devices for a 16GB white iPhone 4S. Users facing hardware related problems with their 16GB iPhone 4s were essentially given free upgrades to the Siri, A5-chip, 8MP camera-packing iPhone 4S. This was until earlier this week: Apple has almost completely caught up with demand for the constrained white iPhone 4 16GB replacements units.

While Apple has caught up with that SKU, Apple is now facing constraints of the black 16GB iPhone 4 and black 32GB iPhone 4 (GSM/CDMA unit breakdown is unclear). Like with the 16GB white iPhone 4 constraint situation of mid-late April, Genius Bars without stock of the black 16GB iPhone 4 and black 32GB iPhone 4 replacements units have been instructed to provide customers with comparable iPhone 4S replacements. Not all Apple Stores are facing these constraints (but many are), and these constraints should clear up within a few weeks if the white iPhone 4 16GB constraint process follows suit here.