Once worlds still change after worldgen, the things thijser says will happen purely because of economic circumstances.
For instance:
Your fort has been trading profitably for many years, making the human civ you trade with wealthy and powerful. This human civ sends out more and more caravans to fatten their coffers, which leads to the destitute elves raiding the caravans in desperation. As a result, the humans send out soldiers with their caravans to ward off the elves, but the cost of the soldiers is too great and so the whole caravan network collapses. The human nation, thrown into disarray, splits up and villages are forced to forge their own weapons and armour, making such things ubiquitous and supporting the growth of adventuring bands. But these bands anger the natural creatures, causing them to roam about, killing as they go. In the wake of these creatures, civs start to fall and the goblins move in, looking for a slice of the pie.
In the above scenario, you go from normal DF, to an age based around the mastery of trade and stock trading, through to an age of weak, poorly armed soldiers, then to small groups of hardened, well armoured soldiers. After that, you nee to completely refocus away from your economic fortress and focus on defending yourself from greedy adventurers, fewer in number, but a vast, mixed bag of skills and equipment. Then natural creatures are the order of the day, glass cannons, somewhat, leading you to increase your meat and leather labours. Finally, growing wealthy and powerful on the rich supply of prey, you enter the age of large, well equipped armies, militia no more, formations and global conquest.
Sounds like enough development for me.