Family Guy didn’t predict shit.
Homophobia is directed at straight people too, to remind them to not be like us, and sometimes it hits a straight person who is actually not straight and just closeted. Transphobia is directed at cis people too, to remind them not to be like us. And so many trans people have early experiences while living as the gender they don’t identify, managing every little behavioral tick so that no one would guess that they were trans. Sometimes that’s for fear that everyone would actually believe it, and then the transphobia would never stop. Sometimes it’s just because even worse than transphobia is the transphobia you face before even getting to transition, the transphobia that teaches some of us to never transition. I know too many people who have chosen to never transition because of this.
So: Family Guy didn’t predict shit. They lashed out with their usual transphobia, one of many shows to make a joke that is simply the declaration that some cisgender celebrity is really trans. The joke works like this: we (assuming the audience is all cis people) can see what you really are, and your gender is a lie. Hah! What the show did is little different than the asshole straight guy who harasses other guys to remind them not to be faggots, and one of those other guys later comes out as gay. What the show did is different because it was on TV to a very wide audience, with a context of punching anyone who doesn’t laugh at their jokes, with an audience who liked the feeling of being able to give no fucks and liked the easily repeatable silly one-liners.
But if you really feel like they predicted Caitlyn coming out, then think of it as: they outed her. This is one of the biggest ways cis people try to enforce power over trans people, by outing us, by threatening to out us. I mean, jeez, one of the more pervasive things I’ve encountered in trans fetishizers is their arousal at the idea that they will be the one to know my little secret, as though it is a secret in the first place. And this is why more and more trans people are being out and visibile, and talking about being trans: for most of us it’s not about educating, it’s just about controlling our own narratives.