I think AMS is pretty safe, given the KL/AF/DL tie-up and anti-trust exemption. AMS is more efficient than CDG, and far easier to navigate. Can't see it going away unless AF decides to downsize AMS and move much more operations to CDG. I don't much see that happening.

Recall that FRA was created as a hub back when it was harder to get international routes directly from the States, and back before alliances became as ubiquitous as they are today. TWA used ORY, IIRC, keeping a fleet of 72's that operated to various European cities, which were fed by larger aircraft from the States. There are now enough long-haul aircraft operating directly from the States (and various new agreements that allow that) to reduce the need for something like FRA as a European hub.