As for customer loyalty, Verizon recently noted something similar to what AT&T has said before: 80% of new iPhone sales are to previous owners.
So basically the carriers have built up a core iPhone user group that they can depend on to keep buying for themselves and their family.
At the same time, Android phones are selling about twice as fast as iOS phones, so intuitively it seems that new customers are going that way.
Umm, the report was that 80% of Verizon's iPhone sales were to
existing Verizon customers,
not existing iPhone owners. It's about how many are switching carriers, and said nothing about how many were switching platforms.
However: Since Verizon has offered the iPhone for less than a year, that means it's a pretty safe bet that practically all of that 80% who were already Verizon customers were upgrading from something
other than an iPhone -- which is quite the opposite of what you were saying.
The iPhone market is still growing by leaps and bounds, as today's other news stories also indicated.