Science has had countless cycles of believing we had discovered, more or less, all that was to be discovered and the remainder would come in sorting out things to another decimal place. Then a revolution, sometimes in short order, sometimes centuries later, comes around and emphasizes our ignorance and arrogance.
So at any given point you have two options: that we've finally reached "the end" - this is it and we can go no further. Or that we're at yet the latest cliff-face searching for that ever-elusive path through. I would always bet, hard, on the latter. At least if I could live forever, because even if I am right there's every possibility, if not probability, that none of us living today will be around to see it shown.
The notion of being able to discern all the fundamental laws of the universe while living on a single isolated grain of sand in a beach of ever more bizarre discoveries stretching out endlessly in all directions just seems improbable to me, at best.