Man, i've been thinking that for a while and you put it very intelligently...the theme of convolution between hero/villian, light/dark were so apparent in TDK, it would seem totally feasible to NOT have a primary antagonist (considering that would be the batman). They (the corrupt gotham police force since dent is no longer in the picture) will hunt him down like an animal...somewhat similar to "the most dangerous game". Rolf, i think that would totally work and i stand by you 100% dude. Although, i could envision a situation in which some of the corrupt cops being unsuccesful in apprehending the batman would hire some 'outside source,' possibly deadshot as a secondary antagonist.
		
		
	 
 
Yes, a secondary antagonist, the main antagonists are the police, the police who allowed the unbearable corruption griping the city to exist, in fact the police are just as bigger threats as the crooks who pay them off, without their greed the mob would never exist. They must be the next villains, as they are responsible for most of Gotham's problems.
 
Yes, you can have one or two secondary villain, maybe the Police hire Deadshot to kill Batman as you said. And we can have another villain in the opening scene, like the scarecrow's little scene in TDK, maybe Batman crashing one of the Mad Hatter's insane tea parties. Or a sequence of Batman decodeing one of the Riddler's riddles and capturing him.
 
Q) Will they actually do this?
 
A) They might consider it...
 
Q) Will fans like it?
 
A) Most of them? Probably not.
 
Q) What will happen if they do it?
 
A) People will be unable to look past the lack of colorful villain running around causing mischief and ignore the fascinateing story that would be told. The movie would be accused of being incredibly boring and Warner Bros would fire Nolan and give "Batman 4" to the next Joel Schumacher.
 
Q) What will happen if they dont?
 
A) They would create a main villain as fan service who does not fit in to the movies theme and story and he would be played poorly because Nolan didn't want him. Everyone would hate the new villain for his out-of-placeness and his rushed interpratation and Warner Bros would fire Nolan and give "Batman 4" to the next Joel Schumacher.
 
Every which way we lose.