Yeah, I think the main factor here is repeat viewings. A dead month does not guarantee that CA:TWS will garner repeat viewings, and just because THG:CF is dropping in T:TDW's third weekend doesn't mean that people will stop going to see T:TDW again and again. I'll point to Skyfall, whose theatrical run was greatly challenged by both the last Twilight movie and The Hobbit, and still made 300M domestic and over 1B worldwide. (I know, it's not a perfect comparison in terms of what markets were being catered to, but I still think it's a valid one.) In the end, my point is that these movies can, should, and will perform on their own merit, whatever their competition.