Three other examples of convergence theories are Roko's UIV, Hollerith's GSZ, and Omohundro's "Basic AI Drives".  These also postulate a process of convergence through rational AI self-improvement.  But they tend to be less optimistic than CEV, while at the same time somewhat more detailed in their characterization of the ethical endpoint.

I wouldn't say that any of those three are "less optimistic" than CEV; GS0 and UIV are just competing normative proposals, and the AI Drives are what you get out of most self-improving goal systems by default, and can be overridden. (And CEV isn't about optimism anyway — it's a goal, not a prediction, and in that capacity, it's actually fairly pessimistic, going by the variety of possible failures it tries to account for.)