1) It's the final chapter. Seeing as its predecessor is the third-highest domestic grosser of all-time with $533M in the bank, unless TDKR is a critical mess (zero chance), you can expect it to at least match that figure. Find me someone - anyone - who doesn't want to find out how Christopher Nolan closes the chapter out.
2) The kiddos are out of school. TDKR's release date is July 18th, a Wednesday smack-dab in the middle of summer - meaning kids are on vacay and able to flood theaters for all showings, every day. For the first few weeks, expect grosses of $20M+ on weekdays in addition to the whopping weekend numbers.
3) It's more dangerous than 'The Avengers'. Now at first that might appear to be a detriment but there's something alluring about the danger factor. Whereas 'The Avengers' antagonist, Loki, bordered on cartoonish, Bane is straight-up malevolent - we aren't quite sure what the muzzled dude is capable of. The power of the unknown is palpable.
The one thing TDKR has working against it, Nolan's refusal to convert his film to 3D, which would have padded the take with the surcharge for third dimension viewing. That issue aside, by the time TDKR is unleashed, the buzz will have built to proportions not seen since well, The Dark Knight. Avoiding it will not be an option.