πολλῶν -- gen pl. "of many things"
ὁ καιρὸς -- masc. nom. sg. "the right/critical time"
γίγνεται < γίγνομαι -- third singular present indicative "[subject] happens/come to be"
διδάσκαλος -- "the teacher"
Because γίγνεται isn't from the second principle part (which is γενήσομαι), I disagree that the translation is "will turn out to be" -- instead I would say, "turns out to be" to make it present
I'm going to ignore πολλῶν for now -- ὁ καιρὸς γίγνεται διδάσκαλος seems quite straightfowardly "the right time happens [to be] a teacher"
I can see where πολλῶν goes with διδάσκαλος to make it "teacher of many things"... but then, I ask, why not just write ὁ καιρὸς γίγνεται διδάσκαλος πολλῶν?
(I do think Greek word order does matter a bit, despite what everyone says.)
So I actually think that this should read "From many things [read: experiences], the right time turns out to be a teacher."
I'm not beholden to my point about πολλῶν, though, but this is what I think.