This is more of a case of the WB wishing it had what Disney/Marvel has right now with movie success. If it's a war it's a really one sided affair so far.

Man of Steel was a hit. Not a juggernaut hit like Avengers but it did solid box office. I have no doubt that any Marvel movie that gets released in the same week would hurt both movies since the audience would be divided. It would be bad business for both. I don't think it would matter who won. Both would be losers.

Thor 3, Dr. Strange,etc...would the WB be dumb enough to risk doing severe damage to their important expansion plans with Man of Steel 2? I say the WB is playing chicken to get Marvel to announce early what goes in that slot and moves Man of Steel 2.