Yes, according to the Clevland Clinic, "your EF can go up and down, based on your heart condition and the therapies that have been prescribed".
You can read more about Cleveland Clinic: Understanding Your Ejection Fraction (EF).
Only you and your doctor will know if it is still recommended to have an ICD (implantable cardioverter defibrillator) or other specific treatment, as according to the American Heart Association, "long-term prognosis varies depending on the cause, severity and degree of functional impairment". Your specific condition of DCM, along with specific treatment options, can only be determined based on the cause (if known), as well as severity and other medical conditions you may have.
Since EF can go back down (and can go up as well), does this information help you in your decision-making? Do you have any further questions we can help answer? When is your next appointment with your doctor, and what has been recommended now that your EF has gone up?