Illini fans have been teased and fooled so many times in the last 20 years - especially the last 13 or so. I don't think we'll see any meaningful movement in attendance (50,000 or more) until we have at least back-to-back bowl seasons. And attendance always seems to lag on-field performance by at least a year.
As Robert said, I think we're down to the "core" 30,000 or so that will try to attend no matter what the team looks like. It takes more than hype - actual results to drag in anyone else on a regular basis.