I just can't see the audience that is used to Iron Man or the new Batman movies going in for a movie about a teenage kid who gets a magic ring that transforms him into Captain Marvel when he shouts "SHAZAM!" I for one would be making fun of it and comparing to Kazaam!
I'd kind of expect them to call it Shazam, anyway, not Captain Marvel. I don't think there's been a thing with him since the '70s where Shazam! wasn't used in the title in some way or another (sometimes people just straight up call him Shazam as his name...)