I don't think anything official yet, just 'unofficial' sources saying that. But those 'unofficial' sources are coming from respected journalists, so might have some weight.
I think that the survival/base building genre is just getting started. Rust/Ark/Exiles shows that there is a demand for such games, but IMHO no one has gotten it right yet. Each of those games had a lot of potential but was deeply flawed in execution. Fallout 4 base building was more or less tacked on to the game and never really worked well. It sounds like they are going to flip the game, making the base building the core of the game and the adventuring just a way to support that. Perhaps they will add a bit of city-management in there too as your base grows into a town? If they can manage nail the base building aspect it could be a good game.
I would not bother wasting money on the F76, it's buggy incomplete and nothing for the single player, so waste of money IMHO, as to F4 building wise it was pretty good, reason being there are a wide range of add-on nexus mods for building, I just upgraded my F4 to GOTY version and downloaded Snap and build mod 2, scrap them all, bridge fix at sanctuary mod and having a lot of fun with F4, it's like a new game will all DLC, houses you can build actually have windows , marble stairs/walls or floors(with different colours) no problem with this mod and houses look brand new rather then those crappy sheds/shackles.
F4 strength is good single player game( F76 does not come close) and the mods you can get, they pretty much cover all bases, you have to hand it to the mod developers since they have done a better job with F4 then bethesda could of done.
Nothing hard about base building in F4 , power,food,water and defences and you are all done, add stores to improve happiness.