In twilight of 2013, Nintendo put out a remastered The Legend of Zelda: The Wind Waker for Wii U. One of the key reasons cited for the project's existence was it allowed the Zelda team to experiment and familiarize itself with the new hardware before developing the next entry in the franchise.
It seems Bethesda took a similar approach with Fallout 4. Instead of releasing the post-apocalyptic action role-playing game alongside the new Xbox or PlayStation, as The Elder Scrolls: Morrowind and Oblivion once had, the studio opted to spend a little more time with the kit before launch.
"The first thing we did was port Skyrim to Xbox One," Fallout 4 director Todd Howard told Game Informer. According to Howard, this was done purely as an exercise to allow Bethesda's staff to understand the new hardware faster than they would making a new game from the ground up.
As for whether we'll ever see that Skyrim port on new platforms, Howard cautioned "don't get your hopes up yet," indicating nothing is in the works right now while suggesting it might be someday.