agus
I don't know where you got that information, but GPS is universally approved for navigation with the exception of non-WGS-84 areas. That is mostly Russia and PE 90.xx is very, very nearly the same thing. So, if the VORs go out, it might not even be noticed on my piece of kit.
GF
Oh, when the French used to shutdown the TACANs on Friday to prevent us Yanks from leaving Germany and going to Spain for the sun, the F-15's showed them--INS worked just fine to find all those waypoints.