There are a whole lot of things that need to be done before an invitation is extended. The ACC needs to go over the financials of the Cal, Stan, and SMU athletic departments. They need to get ESPN to tell them how much more money they will pay, and that will take ESPN some time because they need to get their number crunchers on it. The ACC needs to send people out to the 3 to inspect their athletic facilities to make sure that they meet the minimum conference standards, and if they don't what are the plans to bring them up to standard. Finally, the lawyers all need to pass paper around, and that is not a quick process because of the number of lawyers signing off on the paperwork. Now, the Big 12 looks like they added Utah, Colorado, AZ, and ASU quickly, but the rumors were that the Big 12 had been in contact with them for months before they started making their moves. For the ACC to get to this point in less than a month is warp speed.