But that's not how modding works.
On the one hand we have modders who want to make just minor adjustments or modifications to the game - like changing something in the UI, bring in some new armor/weapons, swap some textures or models etc. Those can be made with the tools at hand, so that's not a problem. Those are the modders who just want to mod the game which they are currently playing. Those guys could(!) be affected from the Fallout 4 release - but we don't have to worry about that, because we actually have the tools to do this kind of stuff pretty easily.
On the other hand, though, there are the modders/modding groups that have somewhat "bigger plans". Those are the guys who want to add complete storylines to a game, or even do total conversions, like Enderal or Skywind for Skyrim or the things that Steiners Modding Group did with SW: EAW.
Those are the people who want to do something like adding Vizima to TW3, or port Witcher 1 to the new engine or make a TC... and those won't be affected from the release of another game. Most of these people have to rely heavily on the art assets that are already in the game and the gameplay it has; they don't have the manpower (and or talent, tbh) to do this kind of stuff all on their own. That's why you make mods in the first place and don't get yourself the UE4 and make a complete game from scratch.
There's a huge difference between TW3 and Fallout4, in terms of art assets as well as in terms of gameplay. You can't just take any game and make any mod for it - it just doesn't work like this. People who have crazy and good ideas for TW3 right now won't just switch to Fallout when it hits the market, because their ideas might not be suitable for the limitations that the game confronts them with. They will wait and hope for a new RedKit - as do I.
