Both iPhones and iPod touches now display the pink background "This device is expired. Please install a newer version of the OS" activation screen.
Apparently those who have used Pwnage to run the 2.0 Beta firmware are not affected by this expiration since Pwnage bypasses the activation process.
TUAW posts this update on the situation:
"I got bricked as well. Called ADC and they told me there was a new SDK. They said it was still labeled as the old SDK but that if I hovered over the link would show the new one. Not sure how the SDK would fix it vs. a new firmware but I'm downloading it now." I personally can't see any updated SDK material. Perhaps its only available to those accepted into the dev program. Other readers report that they do not see any updates--in the dev program pages or the general iPhone dev center ones.