I don't latch on to many "Next Big Thing" shows (my sheer ambivalence towards Steven Universe would probably earn me the death penalty if tumblr became law) but MAN did I ever get behind Gravity Falls. And yet, because I pretty much never see anything until AFTER everyone else in the world, I'd never actually seen someone else watch it for the first time before. THAT was fun.
Part of me wants to question the logic of cosplaying from a show you haven't even seen yet... but then, the only reason I ever started playing Ragnarok Online was so I could learn the context of my Bard costume (may its ragged, torn up soul rest in peace)
Speaking of which, I still want to cosplay the Summerween Trickster one day.