I'd to see Apple move away from this naming scheme altogether. Just call it the iPhone 2015 (and iPhone Plus 2015). We all know there's a new one every year. The number is getting a little awkward.
I know what you're saying, however the drawback with putting a year in the model name is that as most iPhone models sell strong for more than one year, so having a year written in its name can shorten its shelf life, as it can confuse customers that purchase after the year of launch (for example, if in 2016 you look at an iPhone called iPhone 2105, even though it is the latest model it sorta makes it appear out of date).
Personally, I like the consistency of Apple's naming scheme. We know that the second "S" is always an improved spec version of the model with the same number (usually enhanced hardware under the hood, and sometimes smaller more subtle design changes like when TouchID was added to the 5S for example), but is otherwise all the things you can expect, and will fit your previous accessories for that model (which can also be an advantage).
Generally speaking, the actual number should not be increased (like form iPhone 6 to iPhone 7 for example) unless the actual design has had a major overhaul that is visibly and functionally different (think the difference between an iPhone 5 and an iPhone 6, for example, where the sizing changed, curvature was added, and button locations were changed, along with major differences in how the camera works, etc.).
If Apple's naming scheme was ever messed with, then it would make it much less reliable as to what to expect. For example, the Lumia phones have numerical differences, but there is no consistency with it, and it makes it very confusing. Similarly, Motorola use different letter names, but those letters are pretty meaningless to customers, and we can't really tell what we're getting. The beauty of the way Apple do it though is that it's very clear and easy to understand from the model names which ones are upgraded models, and in what way.
I do agree that the ad that (despite being kinda lame) was still clever marketing, as look how many of us have rushed in to comment on this simple but controversial topic. It's certainly drawn attention to the new iPhone release, without them having to write much.
