Without a sensorimotor apparatus for the brain to manipulate and receive reward-signals from, and thus train to control, there is very likely no "thought" as we would consider it—nothing coherent, no train of thought, no high-level patterns. It's more like the sort of "thought" a foetus would have before its first moment of conscious awareness.
The article also suggests that what we consider to be an experience of physical pain involves certain basic aspects of consciousness that require more advanced postnatal development based on interactions with other people. If this is necessary for physical pain, then more abstract psychological pain would be even further down the road of development. So it's not as simple as whether something is a "real brain" or not, and growing mini-brains from human cells doesn't mean that sentience automatically happens.
Organisms with far "simpler" brains than ours appear to be capable of suffering. I'm unaware of the extent to which human embryonic brain development follows expected principles of evolutionary developmental biology, but if that holds, a sufficiently developed brain should at least be given equal ethical consideration as an animal. Vertebrates are commonly born with a capacity for suffering, so I question how much external input is required. If the necessary brain structures are there, those same structures should suffice for achieving brain-states equivalent to percepts of suffering.
Looks to me like we're not quite there yet, as these cerebral organoids are pretty darn small and comparatively disorganized, but it's only a matter of time before the ethical questions need be faced.
With a little searching, I found similar views from neuroskeptic. http://blogs.discovermagazine.com/neuroskeptic/2013/09/02/th...
Many higher-level vertebrates develop some capacity for "thinking"—that is, for planning/strategizing, puzzle-solving, learning and synthesizing information, forming concepts and abstractions, overriding instincts with beliefs based on evidence, etc. Humans and all other primates do this; as do crows and their relatives; as do dolphins; etc.
But none of these animals start with that ability from birth. "Thinking" has never been observed as behavior available instinctually to any animal. A newborn crow or gorilla, despite being rather self-sufficient with a library of instinctual responses, won't be able to solve the puzzles that we get the adults of those species to solve and which we cite as proof of their intelligence. They grow that ability from months/years of life experience.
In fact, almost by definition, "thinking" is something you have to build: it's a big conceptual hierarchy with sensory data at its base. And—as far as we know—instinct can't pre-bake the needed raw sensory data into brains. (It can bake in higher-level associations, like scent- or pattern-associations for predator avoidance. But it doesn't include these in low-level "raw" terms where a brain can derive any of its own interpretations or abstractions from them.)
Without accumulated experience, a brain is still experiencing the world, and reacting to the world, and experiencing reward signals from the world—like most animals do—but is not yet thinking about the world. Thinking is a matter of updating beliefs about schemas/models/concepts; and those things only exist when derived from sense-data "evidence."
If this tech evolves, I'm really worried about brain harvesting or trafficking, we already have increasingly desperate people turning to organ trafficking, and human smuggling is tied to organ harvesting.
http://www.reuters.com/article/us-mideast-crisis-syria-traff... https://www.decodedscience.org/organ-harvesting-human-traffi...
Also, as other comments have pointed out, these organoids don't really have any neural inputs, so it's unlikely that they're wired in a way that is at all analogous to real human brains.