They're going to wait for people to forget and then try again with a new game that doesn't have a large, established community. I doubt it'll be Fallout 4 -- Bethesda's press release a little while ago threw Valve under the bus on this, and I doubt that they're going to want to touch the idea with an 11' pole now.
How so?
In our early discussions regarding Workshop with Valve, they presented data showing the effect paid user content has had on their games, their players, and their modders. All of it hugely positive. They showed, quite clearly, that allowing content creators to make money increased the quality and choice that players had. They asked if we would consider doing the same.
"It was all Valve's idea, they came to us and told us it was a good idea that would make things better for you!"
Three years later and Valve has finally solved the technical and legal hurdles to make such a thing possible, and they should be celebrated for it. It wasn’t easy. They are not forcing us, or any other game, to do it. They are opening a powerful new choice for everyone.
"Valve were the ones pushing to get it working!"
Opening up a market like this is full of problems. They are all the same problems every software developer faces (support, theft, etc.), and the solutions are the same. Valve has done a great job addressing those, but there will be new ones, and we’re confident those will get solved over time also. If the system shows that it needs curation, we’ll consider it, but we believe that should be a last resort.
"...because they were their problems to solve, after all."
The remaining is split 25% to the modder and 45% to us. We ultimately decide this percentage, not Valve.
This was the only point where they admitted fault at all, and then they proceeded directly into further damage control a la:
This is not some money grabbing scheme by us. Even this weekend, when Skyrim was free for all, mod sales represented less than 1% of our Steam revenue.