No offense, but I really wouldn't want Fallout to turn into a survivalist game; it's fun because it lets you play with "modern" technology in a post-apocalyptic setting. Running around with one-shot flintlocks and crossbows as primary weapons wouldn't be much fun for me. Stuff like that is better left to TES.
Agreed, but my point stands that 200 years are far too long for high-tech weapons to still work. Hermetically sealed ones, yes. Well-kept family heirlooms, sure. But otherwise, the simpler the better the chances to keep on gunning. In Fallout1+2 jury-rigged devices to fire pre-war ammunition were rather common, energy weapons were rare. Where they were available, they were either unique items salvaged from pre-war installations, or imported from the Enclave. The best somewhat common hightech-weapons were railguns and 1990's weapons with caseless ammo.
In the current Fallouts you get your hands on energy weapons everywhere, even the ammo is cheap and commonplace. Even when people aren't capable of building their own power plants using the available resources (sun, wind and brahmin dung) someone ought to have made use of the seemingly unlimited supply of Microfusion cells before fighting wars over an antique solar power plant and an even older dam.
As for modern conventional firearms - we use them along wiith weapons in WWI and Civil War design, and the ancient gunpowder weapons stick with the modern weapons just fine. That was my point with the firearms: It makes sense that the ancient weapons are "so good" when you assume that the modern weapons suffered very badly from those 200 years.
200 years after civilisation's end, people should long have ran out of pre-war weapons and ammo. So either they continue fighting with sticks and stones, or improve civilisation to a point where they are able to produce pre-war-style weapons in (Yes, I know that the Gun Runners do it.) But if they have that technology, they should no longer need to covet pre-war artifacts.
Long story short: In either case the Fallout we know has to end after 200 years, it either evolves into a preindustrial survival game, or into a SciFi variant of The Settlers. (That said, I'd prefer a Fallout set in the 2170's)