We plan for the upgrade to Android 4.0 (Ice Cream Sandwich) for Galaxy S II customers to be live very soon. Like with every OS update, we test it on our servers before we roll it out to customers. We’re in the process of doing that with Android 4.0 (ICS) for Galaxy S II customers and hope to make that live soon. We recommend customers wait to attempt the update.This extra testing phase that AT&T is taking for the update shouldn’t last too long and I wouldn’t be surprised if the update is live again in just a couple of days.
source: Android Central