What's going on with the portal though is insanity and it will destroy the sport. Coaches in essence have to re-recruit their roster every single year. That plus unregulated NIL $ is a recipe for chaos. You don't see unrestricted free agency or open salary caps in the NFL do you?
It's going to affect every team in the country to some degree. I think the volatility is more likely to help an ascending program like Illinois more than hurt it. Coach's jobs in the off-season are certainly more difficult than they were previously, but the ones who adapt effectively will be rewarded on the field.
Teams that have struggled to get results will struggle to keep the few good players they have. Teams that have managed to stockpile depth and talent, will struggle to keep it all, but will keep the guys who think they are going to play. (This isn't a new development. It's just a little easier now) A team that has shown the ability to develop players and has snaps available will greatly benefit from the portal.
Now that the Illini have leapt back into relevancy in the B1G, can they sustain it? I think so. I think BB will find a lot of answers via the portal.
I don't think there is any real threat of NIL and the transfer portal "destroying the sport". It's just going to make things more volatile, and for a lot of fans, more interesting.