We don't really know what this year's phone will bring. And I'm getting my doubts that it will be called a 7 if it still looks like a 6. Maybe 6se?
But if it isn't a significant improvement over the current models (I'm still on the 6), it may push me to try the + model (with mid level storage). If it turns out too big for me over a year, I can hand it down to someone else in the family running an older model, and who carries a purse. If I like the size, and just HAVE to get next years' model, I can buy that one with full memory, etc.
Or just keep it, and now be on the 's' line. Second year of a model, compatibility with cases, etc, but the models that have more of an internal improvement.
It seems that, historically, the 1st model of a generation from Apple has had shorter support from Apple.
Original iPhone. 3 OS versions.
3G. 3 OS versions. And it was really lagging.
3GS. 4 OS versions.
4 4 OS versions.
4S 5 OS versions.
5 5 OS versions at least.
5S 4 OS versions at least.
It seems that, the S model is when the life bumps up. At least for the 3GS and the 4S. For the 5 and later, since there hasn't been an EOL done yet, we don't know whether the 5S will bump up to 6 years or not.