Nintendo needs to follow Sony's lead for a change and make a phone version, a slider similar to the Xperia Play. Put Android on that and release a refreshed version every year or so. Games must be backwards-compatible for at least 2 handheld generations, so two years. Beyond that is up to the developer.
The era of long-lasting handheld generations is over, ultraportable chip technology is moving too fast and people aren't content to use the same thing for 3+ years. Not to mention that people are getting used to only carrying around one device all the time.Make a 3G version and a wifi version, keep the dual screens, have similar controls to the 3DS but with a second analog pad on the right side. Release it priced under the assumption that at least two games will be bought, at which time the sale breaks even and beyond that there's profit. The games are download-only and cost $19.99 at the maximum. They must be tied to your account, not your device. $250 for the wifi version and $50 for the 3G (on contract)... sounds good to me. Oh, and, BATTERY LIFE for a change!