Examines the potential effects of policy changes on (1) the growth of Medicare's managed care program, (2) employers' attempts to administer their respective benefits seasons, (3) taxpayer savings measured against beneficiary protections, & (4) the resources needed by the federal agency that runs Medicare's day-to-day operations. Because a specific annual enrollment period could be established without also limiting beneficiaries' opportunities to change to fee for service, it also discusses the effects of the two policy changes (limiting the enrollment period, & limiting disenrollment opportunities) separately. Charts & tables.