BGS is already working on the Creation Kit. Come the 10th, they'll make it more of a priority to finish while also doing any bug fixes or patches they'll need to with the launch of Fallout 4. You are being overly optimistic. It took BGS months to release the Creation Kit for Skyrim because it takes a lot of time and effort. Again, if BGS was just giving players their tools unadvlterated, why wouldn't every developer do it? Presumably it wouldn't take any time or effort. That's because you aren't just getting their tools. Yes, you are basically getting the kit BGS used to create the game, but it has been repackaged for the public. That takes a lot of time and effort to accomplish.
On the PC? It encourages gamers to pick up the game years after it has already released. A thriving modding community always translates into longer term sales and greater interest in a product. As long as players are investing their time and effort into a game that others can take advantage of, it will lead to more consumers buying that product. If the mod kit BGS created didn't generate a single cent for Bethesda, they would never waste time, effort, and money creating it to start.
Except paid mods aren't too controversial for Bethesda as they already tried and stated they would try again with a different model. Actually, Bethesda was going to receive most of the money for the mod with modders only received 25% of the cut IF the mod met a certain threshold of popularity. In other words, modders were going to receive nothing for their work and Bethesda (with a small cut to Valve) would receive all the money unless it was a really popular mod.
Modding becoming a revenue for publishers and developers has nothing to do with the players. It has to do with the mod authors. The whole idea is for mod authors to gain money for their work product that they make available to the public. Paid mods is not unheard of and is not anything new. A lot of mod authors actually want paid mods to be a reality. This isn't just a hobby for some, but a life style. Regardless, mods will cost money eventually for BGS games, but that's not the call of the question for this thread.