Denti
I was thinking of the navigation situation in 10-15 years time when augmented versions of perhaps three constellations, plus ADS-B are available for all to use. With verything working (SESAR and NextGen) it will be possible to fill up a TMA to a considerably greater extent than at present. What "graceful degredation" plan will ensure safety, albeit with reduced traffic flow. Limited retention of things like DME and VOR is one possibility,but there are others, and the whole thing will eventually need to modelled with pilots and controllers in the loop.It is something that FAA and Eurocontrol will have to tackle in combination, but there is little sign of that yet.
Keith