Warners were pushing hard for him to be the villain for TDKR and they still regard him as their best bad guy after the Joker, largely because of how well Batman Forever performed.
So it's likely that whoever gets chosen to write the next Batman movie will have to use him.
I'm not sure who would be the ideal choice to play him though. Most decent actors who can play intelligent psychopaths have already committed to other superhero movies. The ideal choice would be Benedict Cumberbatch of BBC's Sherlock but he'll already have had a major outing as a villain in the next Star Trek. So maybe Jesse Eisenberg, the guy who played Mark Zuckerberg as a gifted, driven, somewhat amoral outcast in the Social Network.
Also since the threat he poses is mostly cerebral, you'd want a second antagonist to challenge Bats physically. My own pick for that would be Lady Shiva since she's never had a movie appearance and offers a different challenge from Bane or Ra's.