Good news, a year after its appearance on the first smartphones (¹), Apple finally integrates a GNSS receiver chipset compatible GALILEO. The iPhone 8/8+ and soon iPhone X are now provided with the LTE X16 Snapdragon modem MDM9655 from Qualcomm company, which includes a multi-GNSS receiver : GPS (USA), GLONASS (Russia), GALILEO (Europe) and QZSS (Japan) (²). Confirmation was given to me by our friends at iFixit.
[Update 15/12/2017] The iPhone 6S and 7 are now compatible with Galileo signals.