There being successful batman flicks before Nolan is not the point, the issue is the style won't be the same. Especially since you have Bale saying he wouldn't play the role without Nolan directing.
Having the main character change between films is just asking for a limited release - or straight to video.
Shrek , Pirates , LOTR, Spiderman - each flick in those trilogies set some kind record on revenue, yet no 4th film. With the possible exception of the Hobbit.