His content is still present in the G.E.C.K. I'm assuming his quests are as well. I wonder how hard it'd be to reimplement him through a mod. Provided all of his info is there to do it properly.
Oh... Ugh...
Spoiler
Earlier on, I was really convinced that it was "Roy" to walk out of Vault 11, but then...
There's not much to work on... And the only two pieces of evidence that are retrieved in-game, do not really connect well.
The "Justice Bloc HQ security tapes" clearly identifies one of the voices as "Roy",
but then there's no way to match "Voice 1" in the "System recording: Vault 11 front entrance" to the voice of "Roy" from the "Justice Bloc HQ security tapes" .
And "Voice 1" from "System recording: Vault 11 front entrance" seems to belong to the one that actually made it out of the accursed place.
Voices of NPCs means nothing, because of technical reasons... The same actor might have voiced both "Roy" and "Voice 1", and that would prove nothing. Isn't it?
Furthermore... Our "Survivor" can be anyone, with anything in mind and we don't know when the facts happened. It can be just dead by the time our Courier Six stumbles into Vault 11.
One of the (few) intriguing side stories, BTW... Albeit incomplete.
Cheers!