I heard we could say The Future Perfect Tense
You will have read in the newspapers about the conclusion of this agreement.
meaning
You must have read in the newspapers about the conclusion of this agreement.
Is it true that we can use "will have V3" instead of "must have V3"?
Yes.
It's very unfortunate that we are stuck with the traditional classification of will do as a "future tense" (and will have done as "future perfect tense")
Really, these are modal expressions, like may do and should have done, with a range of meanings, one of which is futurity. Like other modals, they can have epistemic meanings (about the speaker's or hearer's knowledge or understanding) as well as deontic meanings (about how the world is).
You will have read in the newspapers has an epistemic meaning, something like "I guess/assume that you have read in the newspapers".
You must have read in the newspapers, with a different modal, has a slightly different epistemic meaning, something like "I deduce/am certain that you have read in the newspapers".
