“Expect,” like most English words referring to mental states, is problematically ambiguous. It could refer to considering something (1) likely to happen or (2) obligatory or reasonably due. Speakers may not realize that something obligatory is unlikely (or something forbidden is likely), and listeners can reasonably misunderstand which sense of expectation is meant.
If I say that I expect someone to do something, you’ll probably need context or nonverbal cues to understand whether I consider it likely, obligatory, or likely because it is obligatory. I have some employees who will not be meeting their performance objectives; we expect (meaning 1) them not to live up to their expectations (meaning 2).
Further ambiguity is introduced because expectation is not a single thing out there in the world but rather billions of individuals’ mental states. You and I have different estimates of how likely something is (meaning 1). We are more likely to agree about expectations (meaning 2), although beliefs differ radically on what is “reasonably due” (see: who deserves the most credit or whose turn it is to do housework). A particular person’s expectations (1) are a single thing we can reasonably discuss, as is a consensus estimate (“the publisher expects (1) the game to have 1 million subscribers”). In that sense, it becomes entirely reasonable to expect (meaning 1, personal) something to fail to meet expectations (meaning 1, consensus or someone else’s). I occasionally hear someone say s/he expects (1, personal) something not to live up to his/her expectations (1, personal); expecting disappointment is not fully coherent, but we are just a bunch of social primates with meat-based computers in our skulls.
To answer a recent question: my expectations (1) can differ from my expectations (2).
: Zubon