Thus, the mystery begins. Where are The Final Five? Chen suggests that they'll be released as free apps in the App Store. John Gruber believes that design problems caused the team (specifically, Steve Jobs) to withhold the apps. I agree with John and Brian.
Consider the calculator app. It looks great on the iPhone, as the iPhone is about the size of a pocket calculator. If it were simply "blown up" to accommodate the iPad's screen, it would resemble one of those dollar store calculators with the enormous buttons for older folks. Definitely not what Apple is after. Also, the press release says, "... designed especially for the iPad" (emphasis mine). The five missing apps haven't yet received that loving attention, at least to Steve's satisfaction.
As for getting them on the iPad, I bet they'll be a part of the next OS release and in the App Store from then on. That way, Apple won't be tied to the OS whenever they want to update those apps, and they'll have time between now and then to get them just right.