Big Sky is in no danger of collapse or losing autobid.
It's important to remember that the CFP is not run by the NCAA. The Big school can do what they want and pretty much box out the G6 because they bring little financially. Im not certain that the G6 will get a playoff. Who would bankroll it?
ESPN already has the CFP and I dont know that there is anyone clamoring to spend hundreds of millions to show a G6 playoff. The NCAA could run one but im not sure they wouldn't just force them to merge with FCS and just expand to 32 teams. That seems more plausible than 3 levels of D1 football.
Wisconsin came to D1 late and their arrival came during the mediocre Bjorkman years, so some of their best years came when UND was down, so they were able to build some cushion and UND has seen them less frequently during this down period.
I would say Duluth's titles and hobey baker winners put them in the discussion as well. Having a hall of famer in Brett Hull doesn't hurt.