One mod author has decided to set about the non-to-simple task of porting the entire Fallout: New Vegas map into Fallout 4, with two areas already completed and trailer released, and the results look absolutely spectacular!
The mod author Sir_Bumfrey_Diggles, along with several others who are working on the project, have already ported Goodsprings and Primm over to the game as a demonstration of their work in progress. The map really shines in Fallout 4's graphics engine, and although it's still early days, this could be the start of a really spectacular new mod for Fallout 4.
There's still some issues currently, including details being missing, and draw distance issues, but in concept I think you'll agree it looks great;
The team have stated that they intend not only to port over the world, including all the interior settings, but they then intend to use it as a foundation to write all-new quests set within New Vegas. While porting some original New Vegas quests over has not been dismissed by the team, they are not prioritising this because it would require certain technical challenges with regards to base quests.
New Vegas is particularly popular with fans as being much more in spirit with the original two Fallout games, so it holds no surprise that fans are wanting to re-create it in the newer game engine. Perhaps Obsidian Entertainment will get the chance to create a new entry within the Fallout universe at some point in the future, something they've said they would love to do.