They could if Apple keeps re-releasing the iPhone 4 every year.
The number that keeps Apple up at night is Android's market share, which is more than iOS.
More quality phones like the One and Galaxy series can only add to that share. The One X and Evo LTE are the first phones that, IMO, completely surpass the iPhone 4S in every way. Before, when making comparisons with Android phones that I owned and the 4S, I would have to tell people "Well the screen on mine is bigger, but the iPhone's is clearer." or "The battery life on the iPhone is better." or "The camera and build quality on iPhone is better." My EVO LTE destroys the 4S in every way. Every iPhone owner I've shown this phone to is envious.