"You can never make everybody happy, there will always be people- but I also think people like to be upset, you know? If you think about what’s the show, what is like- what show would it be if it were just “We’re gonna have Star and Marco get together and they will be like so happy”, the end. There’s no show, what is that show? No one would watch that show. So you have to keep it exciting."
Star eternal cuckquean status confirmed! Or at least until the series finale.. And Nefcy says she hopes the show goes on a long time, so she won't pull a Gravity Falls and bail on it early. And it probably will last a long time seeing as they've already greenlighted up to season 4 AND a 2 hour movie, which is unprecedented.
Plus, Nefcy basically confirms Marco banged Hekapoo at 46:30 when asked if there was a thing between them "I don’t know, Marco had a long time to be on his own…" (listen to her suggestive voice as she says this, and the audience going "wooooo").