I don't see a lot of opt outs for the NIT as I think the NET ranking selection was discussed behind closed doors with them beforehand. As a result - those conferences were guaranteed home games, which in turn - brings them one more game of revenue at least. And if you think fans won't show up for the likes of Villanova or Wake Forest - enough will show up.
Indiana and Ole Miss have already opted out. Maybe they missed the closed door meeting that the rest of the p6 ncaa membership participated in.
Then there is Memphis too.