The product will continue to work indefinitely, as there is no "kill switch" or technical enforcement of licensing. Since DX UIM 9.2.0 we have moved to a perpetual license, so there will be no impact to the functionality when the contract expires.
However, the contract is for support and maintenance, so you will be limited only to self-service and community support, and unable to open tickets with Broadcom Support for assistance. You will lose access to Broadcom Technical Support, the Broadcom Support Portal (for downloads), and new security patches or cumulative updates.