The ACC has a very strong relationship with ESPN, and I fully believe that they are pretty damn close to launching a network. Listen to everything that the ACC leadership says, they constantly mention ESPN. I think the setup will be very similar to the SECNetwork where ESPN will own and distribute it, and the ACC will get a percentage of the profits.
ESPN also owns the ACC rights, and I believe are buying back the rights they sold to Fox and Raycom. And ESPN will not allow NBC to get a piece of the action if they believe a network is profitable.
This is a great partnership and neither side will do anything to screw it up. If an ACC Network is profitable for both sides, it will go forward, and my guess is that it will launch in 2017.
If it doesn't go forward, ESPN is going increase the ACC contract by around $2MM per team per year as stated by multiple outlets.
This shows no sign of the ACC wanting to look at other avenues, nor do I think they should.