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Civilization has fallen and risen thousands of times over the millions of years. Resources have been exhausted, regenerated, and exhausted again. Apocalyptic wars have been fought and seen all traces eroded into nothingness. Science has changed beyond imagining (which I will simulate by using the magic and alchemy of a fantasy world, rather than trying to shoehorn it all into some science-fictiony buzzword like "nanotech" or whatever). The remains of civilizations from the distant past have been worn away into oblivion, and the remains of more recent civilizations (ones that will arise millions of years from now) provide ruins to be explored and artifacts of terrible power to recover. Even today, "magic" items created by the alien science of the distant future are constructed by magicians and alchemists. Some can be had for nothing more than ready cash, such as ray guns and water breathing masks. Others can only be found or stolen, or perhaps received as a reward, because a magician cannot be induced to construct them for mere pay.
There can be no question that this will ever be published, however, as it draws on "product identity" items from WotC, such as the githyanki and illithid, as well as such wonderful (and open source) alien beings as the kzaddich and tsalakians designed by John Turcotte (editor of Footprints e-zine) and published in the Swords & Wizardry Monster Book.
Oh, and I've been working on the Terra Ultima setting since long before that upstart Cook announced his science-fantasy offering.