Notre Dame very quickly said they were going to remain independent the last time around. My take, which is worth nothing, is that because they haven't said no, they're still working though the issues.
I would thing that there are some complex negations that would need to take place before they can say yes or no, such as:
(a) how much NBC will pay them as an independent (which depends on NBC to work out something with another conference for programming),
(b) how much multiple networks will pay each team in a Big Ten with Notre Dame (negotiations about which still seems to be in progress), and
(c) what the negotiated cost will be for them to break with the ACC.
Given the complexity, it might be that Notre Dame isn't in a position yet to know their best path, at least from a financial perspective.