ADF as a Backstop
The big problem with GPS is that it is so easy to jam and with the goverment proposing a tax on the free movement of people or road charging as they call it GPS would seem to be the cheapest way to introduce such a tax.
If this comes to pass we will have a great number of people with a very real interest in jamming the GPS system.
So along with the fact that most modern airliners use DME to update the position in the FMS (the B737NG has 5 DME units) I see DME being around for a long time and the logical approach aid to go with this is an ADF located on the airfield as this is the cheapest answer to the GPS jamming issue.
We can also turn this on it's head and oppose the use of GPS for road charging on safety grounds not only for aviation but also for the other safety related uses that GPS has.