I think it's missing a level (SL0.5 - linear) all levels above 1 assumes that the compounding effect of technology will continue into the future, but it's also

I think it's missing a level (SL0.5 - linear) all levels above 1 assumes that the compounding effect of technology will continue into the future, but it's also possible that this growth will level off or come in spurts as major advancements are made, and that the current exponential growth is simply our civilization moving from one plateau to another. At SL3~4 some of the ideas also assume that the space of possible technology/intelligence is a smooth continuum that extends to infinity. However it's perfectly possible (likely, in fact) that faster-than-light travel is simply a physical impossibility, or that there is a ceiling on intelligence which is a very ill-defined quantity to begin with. Bearing that in mind, here is my slightly less optimistic prognostication: Technology will reach a plateau as the low-hanging fruit borne of the scientific method is exhausted. Progress will still be made linearly, with each year bringing less change than the last. Although the total number of minds working on technological problems will increase, the mental effort required to reach the state of the art in very narrow disciplines will approach one human life time. New and exciting technology will be produced, but it will often be the application of existing technology to a new field rather than the result of fundamental research. This state continues for several hundred years, after which linear progress has produced significant results in human lifespan, intelligence or both via genetic engineering and all bets are off.