First off- I should say that I actually don't believe they are going to leave the ACC... Here is a great piece that I read and completely agreed with by @Chaddscott "Why they'll stay"
With news of Louisville informing the Big East its looking elsewhere and obvious unhappiness at other schools in the conference... means the following scenario could still come about but in a slightly different fashion because now Notre Dame needs to find a place for its olympic sports with the Big East unravelling.
But... If Florida State and Clemson leave for the BIG 12... while disappointing, it will serve as a red carpet to the Irish. The ACC will be way more desperate to land the National Factory that is Notre Dame, and Notre Dame will use that to their advantage in negotiating their terms for entering the conference as a full member.
1) Modified individual tv revenue contract (allowed to have own but certain percentage to conference, tiered rights)
2) ACC must take Navy (at least in football)... *the irish would have a 9 game conference schedule that now can include their rivalry with navy, therefore leaving room for their game against USC and a big ten opponent (more on navy at the end).
3) Football division alignment changes for scheduling... The Irish brand is the eastern seaboard, midwest and SoCal. They serve the midwest with its home games and a non-conf big ten matchup. SoCal is served with its annual matchup with USC. Now the interesting part- Besides Navy, the 6 ACC schools that ND has the most interest in playing every year would be [rivalries] Pitt, Miami, GT and [fan market] 'Cuse, MD, BC(rivalry too). After looking at about 25 different division combinations I felt just one was by far the strongest and school pleasing conference wide. And crazy enough, there aren't many drastic changes:
Atlantic Team - - Coastal Team (Team's permanent cross-divisional rival in same row)
Notre Dame - - GT *An old traditional rivalry renewed... (people forget about the irish history of Atlanta area)
Navy - - Wake *Now familiar (met 7 times in last 12 years)... battle of the smallest enrollment
Maryland - - UVA *People can say whatever, THIS WONT CHANGE... and I'm happy it wont.
Pitt - - Miami *A Big East rivalry renewed... (5 years from now- what's the Big East?)
BC - - VT *No changes here, been like this since divisions were made and both schools happy
Syracuse - - Duke *Private/NonSectarian war... basketball and lacrosse success with turn to football hatred
NCst - - UNC *Yow's mad because they are in the more northern division so I kept UNC with them
-I decided this based on the Irish's preference, power distribution and keeping ACC traditionists as happy as possible. Irish gets everything they want except Miami is the odd team out of their permanent schedule. They still play 2 of 6 years rotating and actually, this rivalry became what it is because of the huge implications of those games. Now the ACC hopes that most of their meetings are in the conference championship game where they belong. As for power distribution, I believe both divisions are very close to equal with Coastal being slightly tougher. Plus this doesnt change much. ND/Navy take FSU/Clemson's spot in the atlantic so the only switch in the divisions was BC and Wake.
Here is why the ACC accepts these terms:
1) YOU GET NOTRE DAME... arguably the most prized football school in the country, and obviously the prestige, academics and other successful sports it brings to the conference. (This more than makes up for losing Florida State and Clemson)
2) ACC becomes the GOOD GUYS of the college world. What has become of college athletics? Presidents selling out long standing tradition for new money and loyalty has no meaning. Bringing in Navy shows that the ACC appreciates all the things people feel have been forgotten in the business of colleges these days. Navy doesnt add money or market... just history, prestige and superior academics, which the ACC wants to rival, if not pass the B1G in that category.
Why Navy? and Why Not Navy?
Navy's academics are supreme, and they have much better athletic success then people realize. Even with their small enrollment, extremely high admission standards and academy responsibilities they have a Learfield Sports ranking of 90, which puts them in front of future ACC member Pitt. Besides a competitive football team they have success in baseball, M/W lacrosse, M/W cross country and track, and W basketball even made the NCAA tournament this past year.
One very "BIG" issue though. Actually it's more of a small issue. Navy has height restrictions for enrollment therefore it will be even tougher to field a competitive mens basketball team. I just dont see them even bringing their basketball teams over to the ACC.... WHICH means Navy will not be a full member and therefore will probably be a football-only member.
So welcome Notre Dame(full member) and Navy(football only) and Rutgers (non-football)
Yes, the ACC has not allowed non full members, but they will allow this (they get ND remember?). Not all schools in the ACC even compete in the same sports (lacrosse and syracuse doesnt even have a baseball team). So why can't Navy be football and another school will take all of the other spots in the conference sports? Two schools come to mind- UConn and Rutgers. School survival is no longer about football in this case. Both these schools need a better/stable home then where they are now, and I'm willing to bet they'd both send their football team elsewhere to get a membership in the ACC for everything else. UConn especially, but I have a feeling BC wont change their minds on letting them in and they will have ND on their side with this one. (UPDATE: Conn gov. wants rivalry with BC... Looks like UConn is pushing hard to mend this relationship and move to ACC) That means it's up to Rutgers. Great academics, AAU member and gives us NJ/NY market. Not a basketball power but the combination of ND/Navy/Rutgers turns out to be a major win for the ACC.