They would go with Grayson/Nightwing before they did Robin...but Nolan & Bale have been pretty adamant about no sidekick in this trilogy. (Now, if they wait a few years after this trilogy, they could reset with the Nightwing character for a new trilogy, but that is a moot point at this juncture.)
It is rumored that Eckhart signed a two picture deal.
Goyer has said that he and Nolan have discussed loosely a theme and villain for the third installment.
http://www.comicbookmovie.com/news/articles/4859.asp
Interestingly, it’s the theme, and not the villain, that most interests me, especially given how the latter seems inexorably tied to the former in this new modern Batman universe. (Fear the predominant issue in “Begins” precipitating the introduction of Scarecrow, escalation in "Knight" similarly calling for The Joker.
The fact that Goyer has a theme he wants to keep in mind for a possible “Batman 3” means he also has a direction, a crisis, and, yes, a villain.
Here are some initial thoughts I had after leaving the theater when thinking about the third act, I mean trilogy (
this will be verbose and stream of consciousness.)
I say
Revelation would be an interesting theme if Two Face is not really dead as Gordon/Batman have cornered themselves by having to play up the mythos of the White Knight Savior angle. (They mentioned it in their dialogue that they bet the farm on Harvey, so the stakes couldn't be higher if the truth were to ever come out.) This could naturally lead to the Riddler who is an obssessive compulsive puzzle solver and Gotham resident. He would have seen the footage of the Joker who posed the question that would set hooks in the psyche of a person like the Riddler. But the Joker left it unanswered for his own hedonistic pleasure: Who is the Batman? (I imagine a scene straight out of the Number 23, Memento or Beautiful Mind with a room full of crazy clippings, information hoarding, etc. The mind games they could utilize for the Riddler could be great.) If Gotham flourishes with renewal after the memorial, then Wayne feasibly could feel that he could put Batman behind him as his intentions have been fulfilled. Just as he is content with letting it go, here would come someone trying to unravel it all with dire implications.
A somewhat re-imagined Riddler would be interesting if they made the him someone who once bought fully into and spread the message of the story and mythos surrounding Dent only to become bitterly disillusioned with discovery of the truth through a series of events (as his mind latches onto all of the potential inconsistencies of the story: Dent would lead to Dawes which would lead to Batman which would ultimately lead to Wayne.) Whereas the Joker was an anarchist who sought chaos for his own pleasure, a person like the Riddler would have disdain for chaos and a penchant for order (his personality demands it), only it would be social order as he believes it should be, perhaps that Gotham's commonman is too easily duped to be trusted with governmental influence through elections (the Dent story case in point.) At the same time he could be attracted to the Joker's charisma and style, hence the similar attempt at flare. If they write him as an intellectual (high IQ scholar, or genius detective/profiler), they could turn him into a political revolutionary who feels the Joker wasted the temporary control he exerted over Gotham. There would be ton of fodder for the duality of nature/psyche, etc.
An interesting cerebral chess match would make an interesting companion to action within the film. Batman was reduced to reacting to the Joker's whims, but it would be interesting to see him have to engage on the offensive as Wayne to stay a couple steps ahead of Nigma mentally. With the threat of Nigma/Riddler unraveling all that he and Commisioner Gordon have built up since Dent's memorial service. The Revelation of the truth would be devastating to the credibility of Gotham's Justice/Political system as well as to Wayne's reputation. Gotham truly could "fall." If Wayne can no longer hide behind the Mask and people associate him with a form of corruption (lying) although it was with good intentions, then everything his father worked for, everything he owns and the reputation of his father's name would be destroyed. That would make for some high stakes in an interesting action thriller. With the exception of Reece, Wayne hasn't really had to try that hard to mask his alter ego. (I think that was just an easter egg if notable at all. But perhaps the Riddler will find it ironic that a man named Mr.Reece knows the identity of Batman and will seek him out.) A film where both Batman and Wayne are one misstep away from checkmate, could be cool to see Nolan-style.