Or something even worse than that ~ I am reminded of this old SciFi story where the folks discovered they were trapped in one of Philip Farmer's "Pocket Universes", and their space ships just bounced off the boundaries somewhere toward Pluto's orbit.
Interesting that the latest theories keep tending toward the idea that what we see, isolated galaxies, linked by gravity in long chains, could very well be independent universes, and these could be interspersed with universes we can't see ~ black matter/black energy, and all of that encapsulated in a macro-universe that holds all of 'em.
I have to disagree with you on that. The universes of which Linde and Kaku are speaking are not visible to us, nor are they composed of dark matter contained in the visible portion of our universe. They're speaking of completely separate universes lying outside the inflationary bubble that we inhabit.
BTW, I didn't know about Farmer's 'pocket universes' stories. Alan Guth, one of the co-discoverers of inflationary cosmology, speaks of 'pocket universes' when describing separate cosmic bubbles.