As seen in other threads, people disagree on whether CEV exists, and if it does, what it might turn out to be.
It would be nice to try to categorize common speculations about CEV.
1a. CEV doesn't exist, because human preferences are too divergent
1b. CEV doesn't even exist for a single human
1c. CEV does exist, but it results in a return to the status quo
2a. CEV results in humans living in a physical (not virtual reality) utopia
2b. CEV results in humans returning to a more primitive society free of technology
2c. CEV results in humans living together in a simulation world, where most humans do not have god-like power
(the similarity between 2a, 2b, and 2c is that humans are still living in the same world, similar to traditional utopia scenarios)
3. CEV results in a wish for the annihilation of all life, or maybe the universe
4a. CEV results in all humans granted the right to be the god of their own private simulation universe (once we acquire the resources to do so)
4b. CEV can be implemented for "each salient group of living things in proportion to that group's moral weight"
5. CEV results in all humans agreeing to be wireheaded (trope)
6a. CEV results in all humans agreeing to merge into a single being and discarding many of the core features of humankind which have lost their purpose (trope)
6b. CEV results in humans agree to cease their own existence but also creating a superior life form--the outcome is similar to 6a, but the difference is that here, humans do not care about whether they are individually "merged"
7. CEV results in all/some humans willingly forgetting/erasing their history, or being indifferent to preserving history so that it is lost (compatible with all previous tropes)
Obviously there are too many possible ideas (or "tropes") to list, but perhaps we could get a sense of which ones are the most common in the LW community. I leave it to someone else to create a poll supposing they feel they have a close to complete list, or create similar topics for AI risk, etc.
EDIT: Added more tropes, changed #2 since it was too broad: now #2 refers to CEV worlds where humans live in the "same world"
0) CEV doesn't exist even for a single individual, because human preferences are too unstable and contingent on random factors for the extrapolation process to give a definite answer.