I used to think there was no way in h*ll the B1G would ever bring in ISU, but that's when geographic TV markets ruled the day. Not as much the case any more and will continue to become less important. If the SEC goes to 16 I don't think there's any way the B1G just sits around and does nothing. I also don't see UNC or UVA as realistic options. Those are deep regional roots and UNC and UVA are ACC bluebloods, unlike Maryland's situation. As much as I'd love ND to join the B1G there's too much historical stink there, and they've already established a relationship with the ACC, if football is going to join a conference I don't see them upending all that and putting themselves through all the pain and headaches of the inevitable litigation. That would make the ACC even stronger and less likely to be poached.
Two most likely scenarios I think are ISU to the B1G, or in a reformed "lesser" conference that's stronger than G5 but not perceived as strong as the other P5s. One reason I think the B1G is a decent possibility is that with the evolution to streaming and away from geographical TV footprints, conferences are simply going to need more athletic content to push out. The location makes sense. And no disrespect, but I don't think a blueblood 'type' university is going to be an option. If the reformed conference happens, I'd think the impact on ISU would be lessened with the CFP expansion to 12 teams, no auto P5 qualifiers, etc. You'd have a weaker conference schedule but load up on P5 OOC games to build the SOS.
If all this does go down I'd hope for ISU to the B1G. I think it's awesome for a state our size to have two major university players in athletics. Why not do the Michigan/Michigan St., Oregon/Oregon St., Mississippi/Mississippi St. Arizona/Arizona St. same conference thing. Would be fun.