Notre Dame will join the ACC as a full-time member of the conference in all sports except football. Notre Dame football will remain independent, but will play five games a year against ACC teams as part of the move, which can occur sometime within a 27 month exit window from the Big East. The conference could negotiate an exit sooner. These are the raw facts as of Wednesday morning.
Now, for speculation:
Notre Dame is now edging slightly closer to being a full-time member of a conference, and that conference is not the Big East. Joining the ACC is a good fit for Notre Dame academically, if not geographically. (As if this mattered anymore, since it currently belongs to a Big East with members entering from the West Coast.) Not that it is shocking, but Notre Dame officially joins the ranks of those who might have suspicions about the long-term viability of the Big East as a major football conference.
As for the implications for the ACC, they are nothing but good. The football team may not deserve the brand, but the brand is what the ACC has tied to their own in this deal. Notre Dame football is highly visible, and with apologies to Rutgers, comes closer than any football brand to being the magical key to the northeastern football market. (Which still may or may not exist, but if it does ND is the way to go.) ACC Commissioner John Swofford secured the conference a spot at the new playoff table last year, and has now brought the Irish into a gentle state of cohabitation with his league. He's paid money for a reason.
For the meantime, the move also means Notre Dame gets to have its cake and eat it, too. It can maintain an ostensible independence in football and keep NBC TV money all to itself while simultaneously horning in on the ACC's superior revenue potential in football. Five games a year allows Notre Dame a good bit of latitude in preserving existing rivalries with USC, Navy, and Stanford, but also allows it to expand the recruiting base by reaching out into ACC territories -- most importantly Florida, one of the three chief talent pools for college football talent, and the talent-rich eastern seaboard.
It is a sensible deal, but also a profoundly weird arrangement that can be read a few different ways. Perhaps Notre Dame is worried about that next round of NBC television negotiations, and wants to diversify its revenue and prepare for the worst. Perhaps it wants a guaranteed pathway for any future playoff claims, which is ambitious. Or perhaps they just wanted what Notre Dame's always wanted: to do whatever the hell it wants, get football money while maintaining its status as an academic power, and be an independent getting its own deals while still belonging to a conference.
Laugh at them for wanting it, but right now that is precisely what they are getting. They'll likely stay with the ACC for a while, too. The entry fees are technically free, but the newly approved exit fees from the ACC are $50 million in American cash.
In short: Notre Dame is not moving in, but they have a toothbrush at the ACC's house and leftovers in the fridge.