It's simple, don't have them fight. Either way, no one would be happy if they do fight. Either batfans get pissy because batgod lost or the general audience's suspension of disbelief and their opinion of Superman is broken if Superman has his ass handed to him by a normal guy.
Why do people expect them to fight to the point of there being a winner? I'd wager that they will start off at odds with one another, but they'll be on the same side by the end. They're not going to fight it out until just one is left standing.
Avengers managed it pretty well, having heroes fighting without a clear winner being decided. When Iron Man and Cap fought Thor, they all stopped after a certain point; audiences get the fights, fans don't get "dissed". Same with Thor vs Hulk on the helicarrier, no clearly defined winner. IF - I say again, IF - Supes and Bats duke it out, there should either be no clearly defined winner.... or if they have balls, should show how clearly, easily and undisputedly Superman would wreck Batman.
I really, really doubt that there will be TDKR-like fight with the same outcome.
That would be countproductive to the purpose of the film – to bring as much money to WB and DC as possible. Big part of box office success comes from fans that go to see the film several times.
If Batman indeed would beat Supes to the TDKR degree – Superman’s fans wouldn’t spend much money on several visits to cinema, and vice versa.
I think that it would be basically repetition of Faora vs Superman fight. Before MoS were released there were rumors that Faora would trounce Supes just like Doomsday did and that he should be happy to stay alive. What we got – nothing that bad, except incredibly awesome fight.
Quote on Comicon were just piar move, to increase the hype (at least in my opinion).