As for this movie being "held up" by the ROTS trailer... nope, not a chance. Every Pixar film has stood its own ground and does better than almost anything else that any studio puts out there. They don't need ROTS trailers to do it for them. Pixar has a huge following. And, my theater didn't show the trailer. Yet nobody left all pissed off and I heard nary a complaint about it not being there. The BO would have been the same for Incredibles even without the trailer.
I didn't care too much for the opening animated short though. I was a bit let down, truth be told.