In his essay, "The Extinction of Man", from the collection Certain Personal Matters (1897), H. G. Wells contemplates the necessary transience of Humanity in the Earth's spotlight and who will replace us when our 15-millenia are up, noting that we would be doomed should the cephalopods make a concerted effort:
Then, again, the order of the Cephalopods, to which belong the cuttle-fish and the octopus (sacred to Victor Hugo), may be, for all we can say to the contrary, an order with a future. Their kindred, the Gastropods, have, in the case of the snail and slug, learnt the trick of air-breathing. And not improbably there are even now genera of this order that have escaped the naturalist, or even well-known genera whose possibilities in growth and dietary are still unknown. Suppose some day a specimen of a new species is caught off the coast of Kent. It excites remark at a Royal Society soirée, engenders a Science Note or so, " A Huge Octopus!" and in the next year or so three or four other specimens come to hand, and the thing becomes familiar. "Probably a new and larger variety of Octopus so-and-so, hitherto supposed to be tropical," says Professor Gargoyle, and thinks he has disposed of it. Then conceive some mysterious boating accidents and deaths while bathing. A large animal of this kind coming into a region of frequent wrecks might so easily acquire a preferential taste for human nutriment, just as the Colorado beetle acquired a new taste for the common potato and gave up its old food-plants some years ago. Then perhaps a school or pack or flock of Octopus gigas would be found busy picking the sailors off a stranded ship, and then in the course of a few score years it might begin to stroll up the beaches and batten on excursionists. Soon it would be a common feature of the watering-places -- possibly at last commoner than excursionists. Suppose such a creature were to appear -- and it is, we repeat, a possibility, if perhaps a remote one -- how could it be fought against? Something might be done by torpedoes; but, so far as our past knowledge goes, man has no means of seriously diminishing the numbers of any animal of the most rudimentary intelligence that made its fastness in the sea.
This passage was probably the inspiration for the "Umbrella Beasts" of Lester & Pratt's "The Octopus Cycle", especially since their nature-finds-a-way-via-killer-whales solution to Humanity's octopus problem seemed a bit cribbed from the ending of Wells' War of the Worlds.
As V. A. Firsoff speculated, land octopuses, especially those that adapt to the challenging environment of the trees -- as opposed to merely hanging around beaches, snacking on sunbathers as Wells imagines -- may indeed have a bright future, perhaps even taking their place among the spacefaring species of the Cosmos. If Wells is right about the danger of them supplanting us, it would be wise to stay in their good graces. Erecting monuments in their honor couldn't hurt.