Sometime in the future you'll be able to explore a higher fidelity version of the world of Fallout: New Vegas in Fallout 4.
Fallout: New Vegas is considered by many to the best of the modern Fallout games. So if you're yearning for the days of exploring the Mojave, you'll be happy to know someone is bringing the entire New Vegas world to Fallout 4.
Modder Sir_Bumfrey_Diggles is attempting this massive undertaking with a few friends, and has already recreated some parts of New Vegas in Fallout 4. As you can see in the video, he's managed to bring Goodsprings, and Primm to the game so far.
It's still early in development, but the goal is to not just recreate the buildings and world, but to use that as a base to write new quests. Bringing the New Vegas quests into Fallout 4 with the mod is not completely out of the question, but Sir_Bumfrey_Diggles says he could only do it with some of the base quests.
Although the modder himself may not port the original quests, he's allowing other modders to use the map if they wish to bring more of New Vegas over to Fallout 4.
The modder has been answering many fan questions on Reddit, and you should head there if you're curious about he has planned.
There is currently no release date for this mod, though you can enjoy the screens here in the meantime.