Battlefield is going through the same paces that Modern Warfare went through when it first came out.
In other words, all the media attention is centred on it and it's being hyped up to be the messiah of current releases, destined to take us to the shooter promised land (am I the only one who remembers back when people were saying how awesome MW2 was going to be? Nevermind the rush of people getting it and praising it when it first came out, along with this being the case when Halo 3 came out, and Gears of War 2 and many more).
Battlefield hasn't so much 'killed' Modern Warfare as it has taken it's place in the great gaming circle of life (cue the Lion King music) and given enough time, it too will be 'slain' by an even newer game once we get tired of Battlefield (and we will get tired of it).