Just like any year, there are those who skip. When the iPhone 6 was released (an astounding success), there were people who skipped because they didn't want a "phablet." Some of the skippers were people who had previously upgraded every year.Imagine how many more sales they would get from people who thought it was worth buying this time around. I'm skipping the 7 this year.
Next year's iPhone is rumored to be a game-changer. Some loyal iPhone fans will skip that one, too. They don't want their game changed.