Specifically the quote from Jack Cabot, after dealing with Lorenzo and asking him what's next?, is:
"Maybe I'll finally travel to the southwest. My father was always convinced that there was another alien city buried somewhere in the Mojave Desert."
Could be alluding to:
Future DLC.
The next game's theme or sub-theme.
It's important to note that it's more than likely is a reference to Area 51 (which is about 80 miles north of Vegas).
Why this line was in the game is more than a small mystery to me. Cabot delivering it makes sense due to the work of his father with pre-historic civilization and discovery of a supposed alien city, but seems needless unless we might pick up this thread later.
Could be nothing, just didn't feel like it, and it is getting relatively little discussion...so thus, the thread.
It felt a little like a precursor for the next game/DLC, like the synth theme with Harkness and Zimmer in FO3 was a precursor theme for FO4. I personally think it could be an allusion to get us back West, whether it be in a DLC (not likely, but still possible) or the next game....specifically near a familiar area of the FO universe (Vegas), and kick the alien theme string in FO into high gear.