So if you didn't know, the gun for the next season is confirmed to be the "LC-10" from Cold war. And my theory is, what if they are adding this gun so that they can add its mastercraft the "neurotransmitter" to the secret cache system.
Think about it, they've been bringing Cold war mastercrafts as free Legendarys for the secret cache system, and we have some legendary that have a different base gun compared to there Cold war mastercraft counterparts like the "RPD – Road Mongrel", but the "LC-10" is too different from the guns we have in the game, so they have to add the "LC-10" to the game, so they can add the "neurotransmitter" mastercraft as a legendary to the secret cache system.