Nope, it’s not going to be required for a device to have a gyroscope. Brandon Watson, speaking on Channel9 says it’s a great idea but it’s not there at launch and an accelerometer is very robust. This is in response to the iPhone 4 having it since it provides greater sensitivity to movement so it’s more precise. See the 28 min mark here. In other notes the compass API will come but not by launch either. And pivot and panoramic controls in the developer tools will come out by the end of the summer. If you use one of the open source solutions it will get published but they ask that everyone moves to their controls when they’re released so that every app gets the same experience.