Yeah, that's a possible marketing strategy to maintain demand in the market place (except that Apple's OSupgrades are almost always reasonably backwards-compatible). But to pull this off, your new processor/OS combo would have to be able to enable new tasks that a reasonably large number people might actually want to do, and that might not be so easy.
Admittedly the advent of g5 telephony is going to sell a lot of iPhones, at least until people wake up to the fact that it's going to be quite a few years before the availability of g5 is much more than merely theoretical and in the near future won't have very much impact on their lives.
Why? Various reasons. Back during WWII the Germans exercised a system of central control over their U-boats worldwide and this required the use of ultra-long wave radio technology because the longer the wavelength the longer distance a signal can travel. Same principle applies to telephony, the g5 wavelength is going to be a LOT shorter than the g4 one. This will translate into a need for a huge number of new microwave towers spaced much closer together in order to cover any given area, and this in turn will translate into the need for a huge capital outlay to establish a viable infrastructure. Don't hold your breath for this to happen any time soon, especially in a country whose government has traditionally shown zero interest in investing taxpayer money to help speed things up.
