Well-timed with yesterday's release of a new Fallout 4 version 1.4.124 Beta with preliminary modification support, an interview on GameInformer.com quotes Bethesda's Todd Howard saying mod support should official come to the released version of the RPG sequel in April. He also discusses testing of the new Survival Mode, and both topics are covered in this excerpt:

You said you are going to beta test Survival Mode. How is that going to unfold?
That’s going to be something different than we usually do. Survival mode has a lot of changes that can be pretty dramatic. Once we get it honed where it’s working well enough, we’re going to put it on Steam beta for a while. ‘Here it is. Start playing it. Give us feedback.’ It’s far easier to update and iterate on [PC]. Once we settle on it, then we’ll release it for PlayStation 4 and Xbox One. We want to get it up soon on Steam beta. It’s not going to be months and months off. If it’s not really working, and we need to iterate on it, it may stay in beta for a month, depending on what we are changing. But we want to make it have the game feel different. The bits we’ve done, and me recently playing it, it’s absolutely some of the most fun I’ve had playing Fallout. I mean that honestly. It changes it in a good way for me, but it might not for everybody.

We’re doing things like you can’t save, it only saves your game when you sleep. You can’t fast travel. There’re all of these diseases. We’re trying it all. It’s a different experience. We’re not trying to make it a ton harder. It’s harder because you’re doing more things. We want the combat to feel different, as opposed to just being a bullet sponge.

When can we expect to see mods, especially on console side?
Our goal is between the first two DLCs. It’ll go up at that time on PC. In April. All of that stuff will go up on PC. People are beta testing it. There’ll be a lag on consoles. We want to get it up on PC and have it work. It’ll probably be a good month before it hits Xbox One, and another month for PlayStation 4.