A ramp attack on the root servers is technically feasible. Signalling the intent weeks in advance of the event could serve 3 purposes
1. ensuring a large number of attackers at the nominated date so as to maximize damage
2. creating fear in the general populace thus raising the groups' profile in the media
3. threatening an attack to cause time wasting and workload concerns for those charged with protecting the root servers, even if no attack occurs
What is certain, if any significant interruption was caused, no amount of concealment (Tor proxies, VPNs ..) would protect the anonymity of the perpetrators from the long cyber arm of the authorities. However, the likelihood of success is low, given their mistaken belief that there are only 13 targets
Anonymous is a protest group lost in a search for a worthy cause.