The civil assessment will become a debt, which will accrue interest and late fees until paid. The DMV hold means that you will be unable to renew your registration or buy insurance until it is cleared. Your license is, of course, already suspended as a consequence of the FTA, and a DMV hold means that the court will not re-instate it until all fines, fees, assessments and penalties are paid in full.
It is unlikely that your local police will come looking for you over a traffic FTA, but if you happen to come to their attention for any other reason you will be arrested. (If, of course, you continue to drive then if you get pulled over you will be arrested and the car will be impounded.)
Richard