Hello, You are right. I have forgotten "will" in my sentence and my questions actually related to the usage of "I will have been asleep" vs "it'll be". I have taken this sentence form an advance language practice book. Following your explanation, which is helpful, I can conclude that one should not use the adjective related constructions (like being asleep, being (too) late, etc. As they themselves as the states can hardly express the idea that something is completed by the time something else happens. Such “idea” is the prerequisite for the Present Perfect Tense to work. Am I right?