The state of Illinois will likely call the bond if interest rates go down and they can sell a bond for, for example, 4 1/2% and use the proceeds to call or retire your bond. This has the benefit of reducing the state's annual interest expense.
Since the US Federal Reserve has announced its intention to not lower, but raise interest rates, lower interest rates are unlikely in the near term. Note that the maturity of the bond is the year 2028; interest rates will no doubt fluctuate by then.
Since it is somewhat likely that interest rates will rise in the short term, it seems unlikely that the state of Illinois will successfully issue bonds at a lower rate, enabling them to call your bond.
Of course, this brings about another question; if you might, because of rising interest rates, be offered a 5 1/2% bond in the near future, why buy this 5% bond? Some considerations may be that if one is paralyzed by indecsion, one has, in effect, bought a 0% bond and a bond in the hand is worth two in the bush.
Of course, the state can retire your bond by income from general revenue. However, if the budget was balanced or in surplus, they wouldn't need to borrow money; that is, sell bonds, at all. As well, Illinois has been struggling with budget woes for several years. A balanced budget seems unlikely.