OH. SO WHAT WOULD HAVE HAPPENED?
Well with Catwoman lined up to appear in her own movie, a new villain(s) would have been drafted in for the sequel. Billy Dee Williams, the original Harvey Dent from Batman (1989) had been promised that one day he would become Two Face in a future Batman movie, so it was likely he would have been given a role.
As well as Two-Face, Robin had been bumped from both Batman and Batman Returns, so he too would have been likely to appear. Oh and another Robin - actor Robin Williams - was linked to the role of the Riddler.