IGN is telling us the earliest we will see mod support for Fallout 4 will be April! PC will be getting the first "official" support (unofficial has been around for quite a bit) and Xbox One should be receiving support in May. PS4 owners will have to wait until June for their support...and that time table is subject to change. It's believed that console support of mods will not begin until Bethesda can ensure it's working properly on PC.
Luckily they've had more than enough testing on that done for them!