There is no infinite growth in nature. Everything will hit a ceiling at some point. So I agree that the intelligence explosion will eventually take a sigmoid shape as it approaches the physical limits. However I think the physical limits are far of. While we will get diminishing returns for each individual technology, we will also shift to a new technology each time. It might slow down when the Earth has been transformed into a super computer, as interplanetary communication naturally slows down processing speed. But my guess is that this will happen long after the scenario described here.
There is no infinite growth in nature. Everything will hit a ceiling at some point. So I agree that the intelligence explosion will eventually take a sigmoid shape as it approaches the physical limits. However I think the physical limits are far of. While we will get diminishing returns for each individual technology, we will also shift to a new technology each time. It might slow down when the Earth has been transformed into a super computer, as interplanetary communication naturally slows down processing speed. But my guess is that this will happen long after the scenario described here.