[JasonB]

I'm not sure it was inevitable. Lewis questioned the decision to take a second pit stop, the Mercedes team said it was a gamble, and making up a second a lap for twenty laps on Max, and then being able to overtake him was anything but certain. I think the key was that Ferrari were so poor that there was no risk of losing second place, so Mercedes had nothing to lose. 

I suspect your departure list might well be fulfilled, and then some. Magnussen and Grosjean are liabilities, Kubica deserved a chance but unfortunately doesn't seem good enough anymore, and Hulkenberg, well he might get a chance at another team who need a reliable benchmark driver. Bottas and Gasly have obviously suffered from being team mates of two of the best drivers around, but haven't even come close to challenging them. We could probably add Giovanazzi to that list, so that's seven drivers whose places are at risk.

I don't know how many promising drivers there are in the lower leagues, but there certainly seems to be a lot of potential opportunities for them to step up to F1 in the future.