Yes, an acquisition program may be terminated while a requirement remains in place. All DoD services and components have identified and documented requirements which, due to funding restrictions or other issues, are not currently addressed by acquisition programs. This is why services, PEOs, and program offices often maintain lists of UFRs (Unfunded Requirements) which may transition to funded programs if conditions permit. In addition, existing acquisition programs are often terminated for a variety of reasons including changes in service or component priorities, threat/adversary changes, or technological changes which support a better alternative.