I just watched the last minute of the keynote. Cook just messed up the timing slightly. It was supposed to be (paraphrased): "...can fundamentally change the world, and I can hardly think of a better reason to get up every morning. [pause] With that, I wish you the best week ever, the best WWDC ever..."
Instead, it became: "can fundamentally change the world. [pause] I can hardly of a better reason to get up in the morning, and I wish you the best week ever, the best WWDC ever..."
Basically, he paused after the "fundamentally change" bit, likely forgetting the final clause of the sentence for a moment. When he remembered it, it came out weird, which he realized, making him panic and punch through the last few lines.
It happens. Steve had the occasional awkward moment, too.