One possible solution is for Apple to sell refurbished devices in countries like India. In the US, the shift to leasing plans such as T-Mobile’s Jump on Demand and iPhone Forever program will make people return their iPhones every time they upgrade.
If these returned iPhones are refurbished, packed and sold again by Apple in emerging countries such as India at reduced rates they would sell very well. This will have two possible solutions:
Apple would not have to develop a low-cost iPhone for emerging markets and risk possible cannibalization of the high-end.
These refurbished iPhones, sold at reduced rates, will not only help Apple boost sales significantly but will help them maintain a good experience for the end users which is very important for Apple’s business model.
While all of the carriers are moving away from subsidizing to on-demand upgrading, all of these returned iPhones at the end of each lease will have to end up somewhere.
This is something that Android or Windows will never be able to do, simply because they don't have Apple's brand strength or smartphones that maintain a high enough resale value.
For Apple, U.S. carriers, iPhone users in the U.S, and potential iPhone customers in emerging markets, this is simply a win-win-win-win.