You can continue on COBRA unsubsidized until your 18 months of COBRA eligibility ends.

In addition, you will have the option to enroll in marketplace coverage when the subsidy ends in September.  Loss of the COBRA subsidy will make you eligible for a special enrollment period (SEP) to sign up for marketplace coverage.  If you make your plan selection before the end of September, new marketplace coverage will take effect on October 1.