411A , I seem to remember that the principles of ILS were German, by Lorenz if my memory is good, and was used during WWII by them.
CATIII GPS is still a long way away and may cost more than ILS, since the US do no need/want CATIII.
A few remarks :
Will GPS continue to be free of charge once the US military have no more use of it ? Will Galileo ( the European GPS replacement ) be free of charge ?
Accuracy is only one of the pre-requisite for a guidance system. Reliability and integrity are others.
The long-range future xLS may well be an hybrid EGPWS/GPS/ Forward looking IR system.