「意気込みのほどが―・われる」「その一斑 (いっぱん) を―・うことができる」
I think of the goo definitions, #4 gets your gist:
To wait in reservation of a good moment to intercede/arrive while viewing the situation.
(my attempt at translating this entry)
I certainly get the feeling that the word is describing the act of waiting in anticipation of an event or time, in a way that is not explicit or alerting. It implies a general sense of vigilance and of reserve. It does not necessarily imply that the subsequent action was successfully performed, but that the preparation of sensibility is being taken and achieved (such as waiting with tact, viewing in stealth, what have you) in order to obtain the result of moving into the next action (which in the case of your example, would be speaking).
EDIT: Wanted to expand because I feel I might not have answered the question in its entirety. I draw my conclusion not only from the meaning in entry #4 at goo, but as a combination of the other entries that pertain to this word. All of the meanings have a similar sense of 忍び寄る, or, to come creeping in opportunely. As I did state before, it does not give me any inference regarding what happens next. Therefore, I think the aspect of the sentence is like your choice #3, where the chance to speak or not cannot be inferred and needs to be more explicitly stated. To get the meaning of choices #1 and #2, you'd want to state it:
He watched for an opportunity to speak, but it did not come.
He watched for an opportunity to speak and then he spoke.