The timeline has been announced as being 2277, in the same months as fallout 3 occured. I highly doubt there'll be any sort of ghoul from the lone wanderers travels, maybe even no passing hints since.. Well, the news would have to come from an overly-irradiated DC all the way to boston.
New vegas takes place in 2278, i believe? I may be wrong on the specific date but its 1-10 years AFTER fallout 3 and so fallout 4. There will literally be no reference at all to anyone or anything from vegas, save for something ominous in all the NPC pvssyr (obsidian probablys set NV after in foresight as to not conflict with any bethesda-run plotlines);

"Did you hear that Vegas survived the bombs? Yeah, me too. Sounds more like a fairytale"

"You seen that courier they been talking about in the NCR? Say he doesn't have a name. Just keeps walking.. Pacing himself between the east and west"

Typhon would be nice.