The big news story will be that for over six decades UFO's have been flying around, violating 'our' airspace, with no respect for our 'laws', interfering with our strategic 'defense' capabilities, and according to some folks, 'abducting' and 'molesting' our people, etc. And the U.S.G. doesn't know who they are, why they're here, or what their plans are; is helpless to do anything about it; and has lied about their knowledge of the situation since at least 1947.
The ensuing media frenzy, and public anger, in the U.S., and to a lesser degree in other nations, toward various parties, including the ETs, could be very disruptive, and even destructive.
Perhaps the National Security Establishment will consider Contact first--see the 'Covert Diplomatic' option in A Real SETI...--so they'll actually have something useful to convey to the American people. If no response is received then the current situation is unchanged--no notification of or acknowledgment to any party or the public is required. [FEB 2017: Barring certain unusual (and perhaps rather extreme) efforts to establish credibility, the CD option may no longer be available to the U.S. See 'Sample Message...'] If a response is received, on the one hand, it forces disclosure, but on the other, interest in the facts of life in the Universe--and, whatever is initially learned, the fact that the U.S. Government is actually 'doing something' about it--may outweigh the obsessive interest in decades of lies by the U.S.G., and the failure of politicians, the institution of science, and the news media to address the UFO/ET presence.
>How Would The ETs Respond?
If the ETs intend contact as soon as humans are ready [FEB 2017: this is known with certainty], and are willing to compromise on the principle of formally communicating only with a 'collective of sovereigns', then they should [will] respond to any CD approach they regard as authentic and credible, i.e., representing an actual message from the head of state, containing a credible promise to quickly deliver the response to the UNSC (UN Security Council). CD allows one nation to initiate a request, and [5/2017
There are several possible explanations for a non-response to a CD operation, such as failure to detect the signal, or inability to establish the message is authentic and credible. These possibilities could be minimized by certain partially overt actions taken as the effort is initiated.
What would they say? One possibility is "We will provide a more substantive response to an open request initiated by a multinational group or the UNSC." Or, more simply: "Open multinational, UNSC, or UNGA initiated." While reasonable in one sense, in that it's indicative of a very 'even-handed' approach with respect to the interests of all nations, it also ensures the process of initiating a request for communications will be 'bogged down', if not buried, perhaps indefinitely, in the morass of UN bureaucracy and diplomacy.
A better option for the ET response might be delivery of one or more data storage and/or communications device(s), which humans could interface with using their technology. The problem, of course, with delivering one or more physical objects, is that some humans, including perhaps most scientific 'experts', would fear infections from ET microbes, and might not trust even explicit assurances from ETs that the objects are 'sterile'. And so the objects might be destroyed, or end up locked in some biological containment facility, and never used. For now, therefore, this is simply not a practical option, unless the initiators of the CD (or other) approach decide in advance that they will trust explicit assurances that any objects delivered will be free of infectious organisms, and request such assurances in the initial message. Absent this, some form of optical communication between a ship and a ground station is most appropriate for now.
The OD (overt diplomatic) national or multinational approach is a bit of a fantasy, unless the announcement is made exactly as the operation is initiated. Otherwise, the rest of the world will loudly complain, and the UN will attempt to assert control, and stop the effort, or at least cripple it with a diplobabble message. Moreover it will force disclosure or acknowledgment, and the world will have to deal with all the resulting social problems, without any useful information from the ETs.
By far the most likely to elicit a response from one or more of the ET groups would be a rational public request from the UN. The most probable response would be a message, and an end to actions solely intended to make their presence known, i.e., the limited demonstrations of presence which have characterized their behavior for decades. [FEB 2017: The ETs absolutely will respond to a U.N. message--but perhaps not at the exact time or in the exact manner requested.]
The UN, of course, has already spoken on the issue of contact. While their response is, on the one hand quite honest and reasonable, on the other hand, it was a rather sad, and perhaps an obituary or even epitaph class declaration of the primitive and psychologically fragile nature of our civilization. [UN press conference video, 13 October 2010.] For now, the UN, speaking for the nations of the world, has sent a message to the ETs--somewhere in between 'go away' and 'sorry, we just can't deal with reality now--if ever'. Of course, this is not news to the ETs.
Forget about it, for now. "The files were destroyed, if they ever existed, the people who created the 'coverup'--if there ever was a coverup--are dead, and, it's all S&M [Sources and Methods]." The S&M tactic--the claim that Disclosure would cause extremely grave harm to the 'National Security' of the U.S.--while total and incredibly stupid nonsense, would be highly effective. Most Americans (and most politicians) will buy it, especially after the Congressional Investigation and the "Commission to Make the UFO Coverup Problem Go Away" are announced.
>"Congress Will Get to the Bottom of This (Coverup)".
Not a chance. Many members of Congress will support, overtly or covertly, the elements of the NSE who were and are opposed to 'Disclosure' (as opposed to simple 'acknowledgment').
Some 'totalitarian' governments have erased their people's history, and it will be seen that this is exactly what the NSE has accomplished. The only practical approach is an 'historical' commission, and even they will never learn anything close to 'the truth, whole truth, and nothing but the truth'.
[FEB 2017: If you're interested in Contact, perhaps you'll consider looking at the Contact and the Future posts (Parts 1-4). Though somewhat dated, most of the points are still relevant. While it's not 'too late' to even consider Contact, the prospects for a positive outcome (for humankind) have grown dimmer over the years, and especially in the last few months.
Only the ETs know the whole story from the larger perspective. They have a wealth of information on the history of UFOs and the U.S.G. (and other nations). The best single source of information on this subject at present is "UFOs and Government: A Historical Inquiry", by Michael D. Swords and Robert Powell (et al.) (see Recent Books).]