"[S]tates and localities are beginning to place more emphasis on supplemental DC plans or hybrid plans as a complement or replacement to DB, while a few states have made the full switch to primary DC plans.... [M]ore public plan sponsors are considering automatic enrollment and other design improvements. While state and local DC plans are commonly referred to as 'supplemental savings' programs, their role is increasing as they are called to cover a growing share of retirement financing and medical costs."