Galileo was based on two assumptions
1 - the premise that the US system (Navstar) will never be upgraded; basically, that the Americans are dumb
2 - EU political independence
1 is dead - Navstar is being upgraded with more powerful sats and other stuff. Selective availability went many years ago and isn't likely to come back because (while it would not affect enroute aviation nav) it would mess up road vehicle nav.
2 is debatable at dubious at best. We all know the USA threatened to destroy Galileo if there was an attack on the USA which used Galileo (presumably, after Navstar got shut down) and I would do exactly that if I was running the USA at such a time. If the people who would actually control Galileo thought that they would be able to just keep it running (unencrypted i.e. for civil use) at a time of real crisis, sticking a finger up to the USA, then they must be unbelievably naive.
And short of a real crisis Navstar will never get shut down because America relies so much on GPS.
Without a covert US-EU agreement on such shutdowns, the project could never get off the ground. But, such an agreement makes a mockery of the political independence argument, of course
As regards the redundancy argument, this can be met using anybody's satellites provided they are compatible at the receiver. Originally, Galileo wan't going to be Navstar compatible - just how thick, stupid and naive some EU officials can be? Make all existing receivers obsolete? Then, some heads got banged together and it is compatible. Which in turn makes it as relevant as the USA putting up more and better sats - which is exactly what (suprise, suprise) they are doing...
The incompetence and stupidity of the people behind Galileo is hard to believe.
More recently, clutching at straws, Galileo broadened its business plan to selling a subscription-based signal which would be used for road pricing. Immediately, people found ways to get around any realistic large-scale implementation - mostly involving cutting 1 wire, or some bacofoil over the GPS aerial.
I would assume that European LNAV/VNAV GPS approaches (where you get a virtual ILS but using wholly GPS) which are coming in in the USA right now, would be predicated on the subscription-based (and higher accuracy) Galileo signal. But it would take another dumb idiot to think money could be made with this. Most of the world's airliners can and do use ILS, which - apart from the landing fee etc - is free. Most of the world's airliners aren't going to fit a special Galileo receiver, with the special decryption facility, just so they can fly LNAV approaches in that little corner of the world called "Europe" when they can already fly the ILS into every airport that counts. Europe would have to rip out its ILS transmitters, as a Galileo revenue supporting measure. Nice one!
Then we can get onto the scenario where an airliner is flying some LNAV or VNAV approach, and the Galileo encryption keys expire halfway down. Or it can't depart, or has to divert, because of some key issue. There are ways around that but it introduces a pointless and serious point of failure, and this has been raised already in connection with this part of the business model.
Now, we are likely to get LNAV/VNAV/LPV via EGNOS and that supplements the Navstar signal. We could have VNAV approaches right now, into every grass strip there is and without ATC requirement, but politics (CAA and NATS) will make sure this won't happen for many years.