New Vegas is not Fallout 4, presumably at some point in the future Bethesda will develop Fallout 4.
As for possible locations, we have an http://www.gamesas.com/index.php?/topic/1108234-official-fallout-4-location-suggestions/ for this. Chicago and New York City are both popular choices, although Chicago has already been featured in a Fallout game so I don't know how likely it is to show up in a new one. Personally I'm hoping to see the Commonwealth and the Institute.