The Defense Department runs the GPS system, and it is obvious that it will take some help from other sources to keep GPS on track to eventually be a sole-source navigational system. The question of electronic jamming of the GPS signals must also be addressed. This affects a lot more people than pilots, too, as the GPS signals are used for timing in internet and cellular communications.
Now you know why Garmin put a VOR and ILS receiver in its popular 430 and 530 navigational systems.
Everyone who has put the effort into taking full advantage of GPS systems sure never wants to go back to the bad old days. But we do have to temper enthusiasm with the reality that the GPS system probably can't ever achieve the reliability of the ground-based systems with their distributed transmitters and diverse technologies. Where in that 1994 briefing the FAA told Flying that the backup system for GPS would be GPS enhanced by local area augmentation and wide area augmentation, that may not come true, at least for a long while. The ILS system will stay around, and the prediction that the shutdown of the VOR system would begin in 2001 not only didn't come true, it likely won't come true in the foreseeable future. The decision that I made to leave the KLN 88 loran in my panel looks better every day.
In reality, the ultimate backup system for GPS might become the ground-based radar system coupled with the retention of some VORs plus the ILS system. And, hopefully, some more satellites will go flying soon.