You're quite presumptuous as he's been dating A WOMAN SINCE BEFORE HE WAS ON TV.

Secondly, how would coming out as gay impact his movie career?
In the same way it impacts all the out gay actors, negatively. It's no secret that in the current climate being openly gay is a bad thing. Look at Matt Bomer. He could have made it big a long time ago. He has everything it takes but there's that pesky thing called being openly gay.
I am not saying Darren is gay, I am just saying that it's really naive to think being openly gay doesn't damage their careers. It's why I admire all the out actors and actresses.
Coming back to where you started is not the same as never leaving. ~ TP

First of all, why can't he be straight if he says he's straight?
Secondly, how would coming out as gay impact his movie career?
Sometimes when I watch Glee I forget he is playing a gay character, so yeah, I think it's more than possible that he's straight.