Would only make sense. The people who won't buy BF3 based on lan functionality alone are gonna go to MW3 to get their fix. That would be a decent number of people, despite how many are still buying the game. All they gotta do is say "we miiiiiight do it, but we'll think about it IF the community really wants it" and watch support for the game roll in.
Teasing a donkey with a carrot on a stick.