I'm predicting they end up as a full ACC member in less than 10 years for a few reasons that you mention. I don't see NBC's contract continuing along it's lucrative path with ND. Their product has diminshed in stature over the years, and granted they have a cult like following, anyone who follows college athletics can see it isn't what it once was. They're still very much a brand name, but moreso in the flagship member of a conference sense than operating at a level above the remainder of D1 college football teams like they have in the past. At one point in time I would have likened them to the New York Yankees or Manchester United of college football - that isn't the case anymore.
The biggest driver I feel is their current athletic department and administration. They keep stating independence, but I almost take it as an appeasement to the old guard. If you look at the path this athletic department and adminstration has taken them on over the past 15-20 years, it's gone from full independence, to affiliation with a 3 game handshake agreement, and now to stronger affiliation with an ironclad 5 game contractual agreement, with their administration publically stating that the status of some of their current "rivalries" will need to be re-assessed. That, to me, is a huge indicator that independence and rivalry are no longer going to trump over everything else.
Either I'm way off, or ND is undergoing a slow, smooth transition from full independence to full conference member.