So, after 5 different worlds and around 20 years of playtime I can further discuss the new trend on fortress life introduced in 40.x
All worlds followed the same pattern, I've chosen a civilization and founded a fort, after a couple of years one of my dwarf became king because all your other settlement succumbed to invaders, eventually a cat dies and the fortress spiral in tantrum. From that point onward every other expedition belonging to the same civ last less than a year because of crazy migrants.
I switch civilization and the pattern repeat, by the time I get to the thirth-forth all of them are overrun by goblin/elves.
Now aside from the matter of playability, witch I consider important because I don't like this trend but I imagine that is all still in the making and that other people may differer, as already shown in the comments in this thread, there are other things that puzzle me.
1)The meaning behind one of your dorf being promoted king is that mountain-homes fell and the former king died, so why don't the settlement turn into the capital?
2)Why do you still get the caravan and the liaison if said capital does not exist anymore?
3)Why the dwarfs in lost cities are hostile if you try to claim the fortress back?
4)While you will always get miserable migrants from a fallen civ(no active settlements on the embark map) if one of yours fortress crumbled during player control(and someone survived), you will not get them if you start a fortress with a civilization that you never had control of but it has also fallen. That seems like a contradiction to me because they should be just as miserable as mine, or that in computer generated/controlled fortress sadness do fade with time, unlike for dwarfs from player generated fortress.
I'm also curious to know if I'm unlucky or that happens to everyone.