They're not going to stay in a league just because they 'own' it if that league is inferior. They have too much pride for that. Of course, they'd like to stay in the ACC as long as it's viable. And they'll do that. But if Virginia, Florida State, etc. start leaving, then they are going to go too.
JMHO, but, neither UNC nor UVA would be the first to leave. FSU would, push some to shove.
If/when that ever happens, it comes down to competing in the cutthroat SEC which does not care about academics or going to a league it views as its academic peers and like-minded institutions. The fans probably do largely prefer the SEC, which will be considered. However, the administration and a lot of the board of regents of the system at-large view the Big Ten as a much more suitable option.
UNC will go wherever the big money people tell them to go. If they say SEC, then, the admininstrationa and BOGs will fall in line.
The Iowa/Wisconsin examples aren't very relevant. In an Eastern Big Ten division, UNC wouldn't be playing in those types of places but once every 3-4 years, and most of the time would end up playing in September or October. They wouldn't be so narrow minded that having to play one football game in the upper Midwest every half a decade would be a reason to avoid what they may consider their best option.