Been a while, but thought I'd bring it up—to question if V is dead or not at all even when Soulkiller'd..
Would it be wise to say V is dead as an Engram, as a copy? Because the way it seems and by taking the real-world perspective into it - if we got our brains wiped and a 'copy' was put in its place, it would still be lights out for us because it's not us - we can only see from our own perspective. Game over, roll credits.
This doesn't happen in our games: V continues on as if nothing happened. We still see it from their perspective, and there's practically no differentiation from 'original V'.
My point is, if V was really dead then the game would have rolled credits the moment they get hit by it in Mikoshi. You cannot experience the conscious being of another, as was extrapolated by the element of the Twins during the boxing quest -- one brother overrode the mind of the other and the two bodies became one person, one mind - no distinct 'two identities' involved. One of them got his end-game credits.
It would have been the end of the game. Period.
Just a thought.
After some time thinking and reading about Alt here in the chat I came to a conclusion... I will sum up some of my points here:
The main antagonist
The main antagonist is Alt Cunningham. Why ?
Johnny is a nuisance at the beginning, but slowly becomes an ally and companion throughout the story and even convinces us to keep our body in the end (coming back to that later on).
Alt lost everything to Arasaka. Her freedom, her life. She gave them Soulkiller, one of their biggest achievements and business prospects. We team up with her, a rogue AI from beyond the Blackwall to free ourselves from Johnny and the certainty of death and fading away. That's the point she becomes the antagonist.
Alt misuses V's desperate situation and hope of being saved to get her revenge on Arasaka and raiding Mikoshi of it's data.
After getting into Mikoshi she destroys it, fusioning all engrams and knowledge into herself and becoming the most powerful AI in cyberspace. V's purpose as a tool has been fulfilled.
V's life expectancy
Alt didn't lie to V and Johnny. The 6 months are probably a valid guess. When we first meet Alt we were connected to the Voodoo Boys' mainframe. She didn't have control over us so she couldn't scan us or our brain. She didn't knew about the DNA reconfiguration progress, but she certainly knew that V was FUBAR already since she knows how the Relic works (probably).
Once we were jacked into Mikoshi, which was controlled by Alt then, she had full control over us and scanned our body and brain. DNA also is just data storage (literally, scientist already stored several terabytes on DNA in real life, look it up) so Alt was able to see the progress of the reconfiguration process begun by the Relics' data.
V's personality and body
This is the interesting part.
The game already showed us how irrelevant and disconnected the body becomes because of Soulkiller and the personality constructs. Vs body can become Johnny Silverhand, Yoshinobu Arasaka can become Saburo Arasaka, people can store their personality in Mikoshi or otherwise powerful storages and can return to life in a different body.
The discussion about V being V or not is futile. The human being is defined by our personality, the mind, our soul, our behaviour. Once a human dies his soul leaves it's body and the body becomes an empty shell. People already stated over past years, decades, centuries that once their loved ones died the dead body was something different, but the human anymore they once knew.
V's chance of being saved would be a new body his personality can claim as it's own like the Relic did with his/her body.
Either that or some other medical miracle which grants overwriting DNA.
The future story
My strong guess would be that a sequel will focus on Alt being too powerful and we have to stand up against her in some way.
The body theory would also give CDPR an excuse to force us making a new character model for the new game.. who knows.
Sorry for the wall of text, but that's something I had to write off my mind.
This is pretty much along the lines of what I expect is going to happen, and summed up the situation of V altogether—I'm anticipating that cloning technology is going to be involved in expansion/sequel content, you summed it up pretty well for me.
[Edit]: One thing that was brought up to me by a friend in the game development industry is that there is generally a rule of thumb involved concerning sequel content - particularly for something within the RPG element, and in this case one that involves multiple endings.
Usually, when a sequel or expansion is intended for the future - in the given case of continuity for a character - the ending is often left open-ended with a common, shared caveat between endings in order to build an opening for the next game (or as few as openings possible for continuity's sake). In this case, it's '6 months left to live', unless you opted to go into Cyberspace.