It can be confusing having two different gun owner cards in Illinois, the FOID and the Concealed Carry license. There have been some efforts to combine the cards, but to date, they are both required.
If you do not renew your FOID, and your concealed carry license is otherwise still valid, your concealed carry license will be revoked. Therefore it is important to renew your FOID card so you don’t also lose your Concealed Carry License.
Update: October 2019: After the mass murder in Aurora Illinois, numerous police forces throughout Illinois have begun to visit the homes of people who have forgotten to renew their FOID cards to confiscate their firearms. If you do not wish to lose your firearms, you MUST renew your FOID card.