Does Apple list any guidelines for how long a consumer might expect to be supported with the version of iOS that ships with Apple hardware at the time of purchase?
On computer OS there seems to be a n-2 support pattern. You can buy AppleCare for 3 years of software support (in most cases) and the previous 2 versions get routine and prompt security updates along with the latest shipping OS.
On iOS there seems to be an n-1 support pattern. You can buy AppleCare for 2 years of software support and security updates seem to be released for the two most recent versions.
Has anyone seen an Apple document or compelling evidence that there is a policy in place for this when considering iOS deployment planning?