Pete Hines has confirmed you will have to download Fallout 4 on Steam even if you bought the disc, but it’s not as bad as it sounds.
@karlemannen ah. no, there is data on the disc.
— Pete Hines (@DCDeacon) October 15, 2015
@Dpl14 @karlemannen yes, though you will still have to download from Steam. The disc doesn't contain the entire game.
— Pete Hines (@DCDeacon) October 15, 2015
As he verified on these tweets, the game is in the disc and you will install it from there, but Bethesda was not able to put the whole game in a DVD. Therefore, you will still be downloading the remainder of the game off of Steam afterwards.
It does make one wonder if game companies are considering the limitations of DVDs for 8th generation games. Could it be possible for future Steam retail releases to adopt Blu Ray? Is that even desirable in this day and age?
In any case, here’s hoping Bethesda takes a cue from Nintendo and allows you to choose to play the install, and a substantial part of the game, rather than have to download everything before getting permission to start playing.
Fallout 4 will be released on Windows, PlayStation 4, and Xbox One on November 10, 2015.