> Can our sci-fi writers come up with something equivalent that is as dizzyingly far from what we know now, as now is from what Aristocreon knew?

By definition we can't, since your premise is that:

> future humans with machines made of materials unimaginable to Aristocreon

So if a sci-fi writer wrote such a thing it'd be deemed ridiculous by the readers of our time.

I once had a sci-fi idea (I'm sure I'm not the first one who came up with this though):

> In an apocalyptic situation, humans decide to encode our whole knowledge base into bacteria DNA so it can be preserved and passed on.

> Then during the process, the scientists find that there is already another species' knowledge base encoded in the DNA, and save the world by utilizing the it.

It's quite far stretched from our current capabilities, but still totally imaginable.