458 The Future Perfect denotes an act to be completed in the future, or (often) a future state:

Εὐθὺς Ἀριαῖος ἀφεστήξει, ὥστε φίλος ἡμῖν οὐδεὶς λελείψεται Ariaios will at once withdraw, so that not a friend will be left us. AN. II. 4, 5. δίκαια πεπονθὼς ἐγὼ ἔσομαι ὑφʼ μῶν I shall have received justice at your hands. AP. 41 e.