And if they come up with an amazing new feature that the previous three years of devices can't support without a hardware change, are they supposed to just hold it for another four years? Especially as they're getting slaughtered in the tech press that they're falling behind and can't innovate and their stock price is tanking because they're not offering said feature?I expanded on this in a later comment, but essentially, for the premium prices of these phones, along with the cutting edge hardware Apple advertises, I would expect mainstream support for at least four years.
Obviously Apple makes no guarantees about any future features, but I find it hypocritical of them to advertise such a powerful device, only for it not being considered good enough a couple years later.