Lots of fuzzy terminology thrown about there - in true heroic architecture style. Granted, I haven't familiarized myself with the finer particulars of "Endless City" but for starters, what does a city make?
Design, intent, ideas? Hardly, at least not as such - "A city is not a tree" (as Christopher Alexander named one of his more influential papers), not merely a hierarchy of structures and functions. All buildings have ecosystems and are intertwined with like and the environment but what amount of human conscious intent can we ascribe to life and still consider it a true ecosystem? Artifice becomes humanity but herein we're dealing with evolution and I'm not at all convinced we can intellectualize ourselves on a vantage point somehow removed of it. Let alone bend it on a ramp.
I've seen buildings where, say, small parks are kept alive on various floors. While natural elements are proven to improve physical health through psychology alone, the overall effect remains somehow a (slightly, but pervasively melancholy) pastiche of a synthesis we currently have only a vague inkling about. Meanwhile, even wayward astrophysicists have constructed very credible models of how cities grow, every which way. It will likely be hard economics, anthropomorphism and technology that will continue to drive the essence of city form instead of aesthetics.
I'm not implying part of it couldn't end up like "Endless Cities", somewhere, but equally I can't see solid grounds why it should. Especially since this seems like a somewhat incorporeal, detached "anywhere" project that one "can" helicopter on a metropolis of a suitable size ("Well, let's put it in London!"). Part of it may even be down to chance distribution of shapes within the "architecture space" of humanity, another perspective where the design-like identity of our being is reframed. Globalization has all sorts of manifestations too and the juxtapositions and tensions of creating (or imposing) instances of physical permanency on almost entirely nonlocal grounds are part and parcel of it.
Unsurprisingly this involves a lot of visualizations most of which never surpass the virtual, floating on a market wherein a limited amount of enablers and environments willing or otherwise prone to be thus colonized meet. We should try to weigh the impacts of the sorts of randomnesses we encounter and perpetrate through building and urbanism very carefully. From the design side Keller Easterling has given this a lot of thought ("Extrastatecraft", to be published).
