So. Dearest Apple. I know you watch these forums. Or fora if you are a Latin scholar.
When you release the iPhone put iOS X.n on it. Where X is the present release for everybody. Where the .n adds the new functionality for that phone if needed. Then spend a month on iOS Y. Y is 1 major release greater than X which also contains the stuff in X.n. Test the bejesus of that and release when ready.