It is entirely possible that if US airlines want daytime HND rights, they must give up NRT-Asia portion in return. UA has all ready dehubbed NRT and entered into a joint venture with NH. Now its DL turn to pull down NRT-ASIA operation.
AC @ YYZ had daily to both NRT and HND, @ YVR NH has HND and AC has NRT. With daytime slots, its possible for a North American city to have both HND and NRT.