The MON will remain until an advanced system emerges that can seamlessly recover from a GPS failure. Until 2014 the FAA advanced a system that provides alternate positioning, navigation, and timing (APNT) as GPS provides PNT. In 2015 APNT research was pushed into NextGens far term, 2026-2030. Once the MON is complete, the FAA plans to re-evaluate existing VORs, but at that point, APNT research will just be getting off the ground. The bottom line: some VOR navigation will be with us for years to come. Youd be well advised to keep your VOR navigation skills sharp.