DF is medieval game and eventually you would run out of things to discover if you stay inside the time frame. That doesn't go well with the open ended nature of the game.
(Deliberately avoiding the evolutionary derail.)
The one thing about Civilisation[1] that annoyed me was the "Future Tech 1, 2, 3..." endings at the top end of the research tree.
DF, of course, is famously procedurally-led, so perhaps there could be an effectively infinite "new discovery" possibility. I might as well at this point refer to the "novel weapons" idea that occasionally comes about. From various components (hilt/handle/strap, chain/pole/chord to connect, sharp/blunt/pointy heads, one-ended or two-ended, one-handed or two-handed, projectile firer and (if so) different
types of projectile, each element contributing qualities (including encumbrance, awkwardness and possibility of self-harm for the untrained) theoretically novel weapon-types (of varying usefulness) could be invented 'on the fly', either by tasking a weaponsmith to have a go at making something or through a mood.
With a similar principle behind it, workshops might be able to be spontaneously developed that create originally impossible objects (e.g. diamond helmets, as a bad example) or even newly procedurally-created object-types as in the possible "two axe-heads on the ends of a chain" weapon the component-based weaponry system might allow for. If siege engines are ever made mobile, putting this kind of wheel on something vital for a fishery workshop and powering it with the bit of a pump a dwarf uses (or some other power source) could make an automated "fish hoover and gutter" that can be hauled to the river and flash-process fish. Or imagine a mining machine moving under its own steam (and made of magma-resistant materials could make for an interesting device, depending on whether you can control it or ensure it stops before it breaches things it shouldn't or topples over the edge of a cliff in the magma-tube).
But I don't want to be prescriptive (or proscriptive), and I just see 'inventions' coming to light regularly, but sometimes they're useless (a bone-cutter-and-polisher workshop (automatic or otherwise) to create low-grade bone-based gems that don't really add value, perhaps), much as with moodcrafted items, and sometimes they're valued beyond measure. It might also need some work to integrate the skill-types available (some dynamic ones, perhaps, developed along with the invention they would use... "Urist McNewfangled the Obsidianiser" or "Urist McUseless the Fluffcollater").
OTOH, does this fit in with the game theme? Not sure. I'm putting forward my 'vision' not because I think it should happen, but merely because if it
does happen, I don't want to end up with deterministic development paths (a tree of development, yes, just procedurally dynamic rather than pre-mapped) and "Futuretech" cop-outs at the end of it all.
edit: [1] Whoops, sorry, "Civilization"...