It is unlikely Apple will adopt USB-C for the iPhone while still using Lightning on their other peripherals and accessories.

“i've always wanted a usbc iphone but i've also accepted in my head that this is apple we're talking about and apple would much rather just not have a port at all on the iphone then give you a usbc option on some of the iphones”

Apple testing USB-C on the iPhone suggests they are preparing for potential regulatory requirements rather than choosing to abandon Lightning voluntarily.

“so the fact that it basically looks like apple is at least testing a usbc iphone to me says they're preparing for if they will be forced to make all of their iphones usbc but i think they would much rather i mean keep going with lightning until they don't need a port anymore”