期待 and 失望: expectations and disappointment
Separate looking forward to a result from disappointment about it, without treating an expectation as a guarantee.
A result still to come
期待, read きたい, describes hoping for or anticipating a favorable result. 新しい企画に期待しています。 means that someone has high hopes for a new project.
期待する does not establish that the project succeeded. に marks the target, which can also be a person, as in 新人に期待する.
Reacting to a result
失望, read しつぼう, describes disappointment when something falls short of expectations. 試合の結果に失望しました。 means that someone was disappointed with the result of a match.
The result is the target of disappointment here. The sentence does not name the players or give a score, so neither should be added.
Meeting expectations
皆の期待に応えたいです。 expresses wanting to live up to everyone's expectations. 応えたい states a wish, not an achievement already completed.
期待していなかったので、失望もしませんでした。 says that there had been no expectation, so there was no disappointment either. Preserve both negatives to retain the emotional sequence.
Does 皆の期待に応えたいです mean that expectations have already been met?
Show the answer and why
No. It expresses a wish to meet them. The sentence alone does not establish whether that has happened.