It might be hard to see it—to see why, but this made me think of the scene in Conan, where Subotai and Conan discuss their gods.
(...And that facial expression that Arnold gives at the end.)
*See... Microsoft now owns the impetus for Fallout, and Bethesda's IP... lives underneath them. Imagine what they could do with that. They can do whatever they want in the PA setting, and claim prior art.

Fallout copies from Wasteland; (though not the retro 50's aspect).
**Not to endorse or encourage it, but Microsoft could make a Wasteland Halo clone with a retro setting; even set it in the same locations near New Vegas—or they could set it in Redmond. They could include the ruins of their Redmond campus. To me it almost seems like buying the land under a landmark.
MS has done similar before... remember that they got started by working with IBM —who had this grand esteem for their own hardware, and allowed Microsoft to own the OS... Only later realizing that the hardware wasn't as important as the OS that they became reliant upon, and they were paying M$ for ever PC they sold that had DOS on it.
***They could make a Bethesda style Fallout-killer... and I don't know if Bethesda could have a case against them. I bet they couldn't even argue against Power Armor.