Here are some random thoughts.
I think the Big 12 gets 5 as OP said...which 5 will change weekly between ISU, OU and Baylor.
If Iowa finishes 6th in the conference which almost certainly means sweeping Minnesota and Illinois in those 2 games then Iowa likely does make it. We will have just beaten both of those 2 teams and finished ahead of them in the conference...because we just beat them. Facts are facts.
I have seen North Carolina play a few times this year. They aren't very good. They will probably make it on their name but I don't think they are a lock. The ACC only got 3 bids in the not too distant past so it could happen.
Looking at the teams vying for the 7 spots per this thread's theme...I don't see 5 teams that are better than the 3 Big Ten teams on that list.