That's one of the things i love about an iPhone, how recognizable it is throughout the years.
Some business experts would agree that having a strong, yet smaller loyal niche customer base will keep a business just a strong as a far reaching one would.
Apple has been catering to those who like big changes but familiar.
Look at Nintendo for example. They are spiraling out of control trying to stay afloat with m$ and Sony. Ironically - both m$ and sony controllers are based off the layout of the Super Nintendo - and they haven't deviated much from it since their first iteration (ps1 / og xbox). Nintendo on the other hand went from the SNES controller, to the n64 controller onto WTF land with their weird designs - and they are paying for it. No body wants to play COD on a wiimote or wii u pad, and because of that - nintendo doesn't get the top FPS shooter games any more, which make a lot of money for the companies.
just a side rant