I think DePaul and Marquette would be dragged along with the rest of their Big East bretheren if it comes to that.
And if they get turned loose, the A-10 will be jumping over them within 2 seconds. If the A-10 gets gutted by the Big East (and I mean gut, as in St Louis AND Butler AND Dayton AND Xavier) and those teams are added while Marquette and DePaul are dumped (extremely unlikely), then and only then will those 2 turn to the MVC. And it's possible CUSA re-enters the picture to add non-football schools at that point.