After secondary tenses the future optative occasionally occurs.
ἐπεμέλετο ὅπως μήτε ἄσι_τοι μήτε ἄποτοί ποτε ἔσοιντο
a. The future optative occurs especially in Xenophon, and represents a thought that was originally expressed by the future indicative. Here the indicative would present the thought vividly, i.e. as it was conceived in the mind of the subject.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].