I think they care about the environment only when it intersects with their financial interests, so yes, ultimately it is about the money. Using renewable energy to power their server farms, etc. makes good business sense given that energy costs are only headed in one direction. I applaud their use of renewables, but I don't for a minute believe it's about the environment.
Unfortunately there's no financial benefit in doing the green thing and sticking with the same size/shape for multiple iPhone models. Better to make each new version a millimeter shorter or wider or thicker or thinner...so the accessory consumption cycle can begin anew.