LOL if you think WB won't rush JLA if Avengers aren't successful. They don't have to beat TDKR and the WB will STILL rush it. They both will do well financially but what's going to happen is this: After about a month after the Avengers is released and closes in around $350M domestically max(sorry people but I can't see it going over that amount), you will start to hear whispers of Justice League Mortal pop up again. Maybe not the same cast or script but you will hear it, I can guarantee it because TDKR is Nolan's last Batman film and they will look to keep that franchise going. MOS will still happen, Batman will be rebooted with a different actor but neither of the actors from the respected franchises will be used in the new JLA film. Why? Because DC characters are to big to be contained into one universe.

TDKR may win at the BO next year, but make no mistake about it, JLA will be fast tracked if Avengers do well.
As a fan of TDK, I'd love to see Bale, Reynolds, and Cavill, along with Bubbles the chimp playing Wonder Woman. Heck a World's Finest movie with Bale and Cavill would probably outgross Avengers. But won't happen because of Nolan.