Its closer to the date. I'm sure its correct now. 2hrs 45/3hrs its not a big deal. JFamis brought up a good point there's never been a 3 hour IMAX film.
I don't know if it was like this everywhere else, but The Dark Knight was so long, and tickets were so in demand here in Portland, the IMAX theater in Tigard (just outside Portland) had to start playing the movie at 8:30am when other movies didn't start until 10, so they could fit in extra showings. It was still selling out in IMAX in September... 3 hours would be really pushing it...
We now got a second IMAX theater here in NE Portland now so that should help, but still.