I don't want see NDB.s closed down
The real question is how much extra would you be happy to pay to keep them?
The Airlines are not interested in NDB, the current generation out of the Airbus and Boeing factories of A380, A320 B777 don't have ADF as standard equipment. It is an expensive option to have one installed for no benefit in first world countries.
VOR/DME probably have many years left in them as the back up, but their days are also numbered.
yanks switch off the GPS
I asked this once at a PBN symposium and was told this was never going to happen as John Doe would never get his pizza delivered. GPS in the US is intrinsically linked to the entire economy, shipping on the inter-coastal waterway, trucking, railways, parcel delivery, taxi operations, farming, road users etc are all so dependant on GPS that it would be political suicide for any party to turn it off. One fact that the speaker quoted was that aviation does not even makeup 1% of the users of GPS in the US economy.