Re: What OTHER elements from The Dark Knight Returns could we see?
Superman's not going to be anything like Frank Miller's version. He wont be working with the government like that.
As for the tank? The tumbler was pretty much Nolan's nod to that tank. Ill say that Affleck's Batman will drive a more traditional batmobile.
I don't think anything will be carried over from TDKReturns other than Batman being older (in his 40s instead of his 50s though) and the potential fight with Superman.
Everything else will be a new story. A good chunk of Returns was used in The Dark Knight Rises so it wouldn't be wise to use too much other than the final act with Superman.