Not if NBC Universal has a say in it ("we're the exculsive weather network on your service or we pull our other channels off")
I don't believe they can do that.
If they could, you would have conglomerates like NBC Universal telling cable/satellite systems they can only carry NBC news & sports network
Weather Nation was exclusive to Dish for 4 whole days until the carriage dispute between Weather Channel & Dish. Since that time, it has been a digital sub-channel for the most part being offered on around 20 stations (plus about a dozen repeaters - mostly in Minnesota).
Personally, I would like to See DirecTV keep both. Maybe then WXIA would replace it on 11.2 with something such as Cozi TV or Antenna TV (currently being offered on WXIA's sister station WATL - 36.3)