While I absolutely loved seeing a character like Marshall was last season--a young gay kid who didn't hide who he was, and who was accepted for it--I also think it's interesting that they are looking at sexual identity from this angle. That is to say, a kid who identifies as gay questioning whether or not he's bisexual. The word "straight" was never used in that promo video, so I don't see this as a straightening in any way. I think it could make for some very interesting television.
So many people in the community identify as "queer," which is what I think Marshall is really saying when he calls himself "I for Independent." It's just rejecting labels.
"You travel alone because other people are only there to remind you how much that hook hurts that we all bit down on. Wait for that one day we can bite free and get back out there in space where we belong, sail back over water, over skies, into space, the hook finally out of our mouths and we wander back out there in space spawning to other planets never to return hurrah to earth and we'll look back and can't even see these lives here anymore. Only the taste of blood to remind us we ever existed. The earth is small. We're gone. We're dead. We're safe."
-John Guare, Landscape of the Body