In the context of CEV, Eliezer apparently thinks that a singleton is desirable, not just likely.

Only one superintelligent AMA (Artificial Moral Agent) is to be constructed, and it is to take control of the entire future light cone with whatever goal function is decided upon. Justification: a singleton is the likely default outcome for superintelligence, and stable co-existence of superintelligences, if achievable, would offer no inherent advantages for humans.

I'm not convinced, but since Luke is going to critique CEV in any case, this aspect should be addressed.

ETA: I have been corrected - the quotation was not from Eliezer. Also, the quote doesn't directly say that a singleton is a desirable outcome; it says that the assumption that we will be dealing with a singleton is a desirable feature of an FAI strategy.