According to the April 13, 2015 announcement in the Federal Register:
This action proposes to remove certain redundant or underutilized ground-based non-directional beacon and very high frequency, omnidirectional radio range Standard Instrument Approach Procedures based on the criteria established by the FAA’s Policy for Discontinuance of Certain Instrument Approach Procedures.
The announcement offers additional details as background:
On June 27, 2014, the FAA published a policy establishing criteria for cancelling instrument approach procedures (79 FR 36576). Cancelling certain ground-based non-directional beacon (NDB), and very high frequency (VHF), omnidirectional radio range (VOR) SIAPs is one integral part of right-sizing the quantity and type of procedures in the National Airspace System (NAS). As new technology facilitates the introduction of area navigation (RNAV) instrument approach procedures, the number of procedures available in the National Airspace System has nearly doubled over the past decade. The complexity and cost to the FAA of maintaining the existing ground based navigational infrastructure while expanding the new RNAV capability is not sustainable. Therefore, the FAA is proposing the following list of SIAPs for cancellation based on the criteria established in the Policy.
The proposal is open for comments until May 28, 2015.
You can find details about the current inventory of instrument approaches and related procedures at the Instrument Flight Procedures (IFP) Inventory Summary website.
To learn more about specific procedures and procedures in development, visit the Instrument Flight Procedures Information Gateway.