I’m going to call it now: Within the next two cycles (I’m really thinking this year), Apple will drop the numbering convention for the iPhone. Seeing as the 5S is really the 7th phone and they’ve already dropped the numbering for the iPod and iPad line, it makes sense. They will probably keep the “C” designation for the colorful-slightly-lower-end one. Plus, it’ll help reset expectations about what’s coming out each year from the “X” model having new form factor and “XS” introducing new internal features. People will be able to refer to which one they have by the year, just like cars, and just like they’ve been doing with the (i)Mac(Book) lines for a while now.