It's just not going to happen. NBC will pony up $20-25 million to keep ND football on NBC and NBCSN and then ND will get its part of the acc money for Olympic sports. They are not going to get anywhere near that kind of money and national exposure by going full in with the ACC.
When the contract is up 2015 - expect to see movement after that - mark my word, you may see extension but ND will go ACC for football eventually.