"But if there isn't any money in it, it will never happen "
That's is entirely inaccurate, unfortunately
Once politics gets stuck in, particularly anti-American politics, and the heads of EADS (a.k.a. France Inc.), Alenia (a.k.a. Italy Inc.) and the other usual suspects can smell a number of Euro billions in govt contracts, the financial case falls by the wayside.
Not that I would complain about more satellites, of course. But will they work with the existing receivers? Will there be an upgrade path for the few thousand KLN89, KLN94, GNSx30 etc owners around Europe? Not to mention the higher number of various handhelds? I don't know.
The last I've heard is that it will be possible to develop GPS receiver chipsets which receive both systems, but that certainly rules out any upgrades short of ripping out the complete PCB. Nobody is going to bother, because with a decent rooftop aerial I already get twice as many satellites than I need for a 3D fix, probably 90% of the time, and I've never lost reception in 500hrs. Apart from a 2-minute bit near Italy when both my GPSs went, and that was clearly jamming.
Jamming, for military practice or for real national security reasons, will jam both systems, and it would be naive to believe otherwise. Likewise for GPS being turned off; there is no plausible national security scenario in which private aviation would still be permitted.
I wouldn't pay any money at all to receive more satellites. In aviation ownership, there are always bigger and more important fish to pay for
The real benefits of a more powerful signal will be in more reliable road navigation (anyone using TomTom etc will know what I mean) and various spinoffs from that. But not aviation. As I've said before, we can have GPS approaches into [insert your favourite GA airfield] right now. Why not? Because of the CAA charges and the CAA requirement for full ATC. Most of the relevant airfields couldn't wait to get shot of the higher-paid ATC staff fast enough.