Before we all know that Christopher Nolan chose to settle Bane (Tom Hardy), which is the least-expected villain in THE DARK KNIGHT RISES, Warner Bros. executives were actually gaming on Leonardo DiCaprio to take on the role as The Riddler instead! That was exactly what fans were aiming for at the first place as well.
Still before Nolan and co-writer David S. Goyer didn't know what the plot would be, or which villains would be chosen in the final chapter of the Batman trilogy, Goyer explained that the ending in THE DARK KNIGHT RISES is exactly what they (he and Nolan) talked about 4 years ago -- which is completely unchanged. When Goyer saw that final scene from THE DARK KNIGHT RISES, he got a lump in his throat.
Personally, I have to salute to Christopher Nolan for being daring enough to feature the least-popular Bane in THE DARK KNIGHT RISES, rather than sticking to the fan-favorite speculation of The Riddler in this final chapter of Batman trilogy. THE DARK KNIGHT RISES hits theaters on July 19.