I actually don't know if they can do this. ISU and UofI have historically had the same entrance requirements set by the BOR. Now, I'm not apposed to all 3 universities raising their entrance requirements - but you have to be careful about not excluding people who actually are capable college students that didn't catch on fast enough in HS (or had a difficult living situation/other events that lowered grades).
If that happens would they limit out of state enrollment more? I could see that as a solution. This is a ways away, however, I think.