I've had a go at retrofitting Fallout 4 into the HTC Vive with the use of certain programs, and I can tell you, it isn't a very good experience. Interesting to experience, but it is very clear specific work would have to be done by devs to get it up to par.
Luckily, that is exactly what is happening. At Bethesda's E3 Press Conference, the publisher announced a drive to become an industry leader in VR, and announced a Fallout 4 VR version for the HTC Vive. It's a huge step for all of VR, as we are soon going to have an honest to goodness AAA game on the platform. That's exciting.
The version of the game is coming in 2017, but nothing more specific was given. I hope it is sooner rather than later.