I feel like this is an overly negative light to paint something fans of your game seem to want. There's an undercurrent of "your wish is bad and you should feel bad" to this.
I appreciate that CDPR has a strong vision for what they want their game to be, but I think if I were one of those fans who wanted to see more of the post-ending setting, I would feel a bit gut-punched by how thoroughly dissed and dismissed my kind of love for the game was.
Having a post story expansion necessitates at least partly re-unifying the different endings of the main game. This is a general problem with sequels already, but it's further exacerbated if you keep the main character the same, which would likely be the case for an expansion.
I wonder what they're doing with the sequel. The easy way out would be to just pick one ending. Not picking one and going all wishy washy is not the best solution either, because a lot of things would be significantly different and it would leave people who haven't played the first game in a weird spot. So I think they will choose a canon ending anyways.
In the Witcher 3 they had a thing where if you'd played the previous game on the same system and the game file was still there you could allow it to read that file and use decisions you made there to inform the new game. Now, I never got around to finishing Cyberpunk and don't know what the different endings are, so I don't know how much of a difference it would be, but if they've done that before they could do something similar here. Like, the world and story are the same, but any reference to the past includes the choice you made. And if you don't have a save file, they just pick the one the developers like most probably.
As long as the main character in the sequel is someone other than V then they could do that for sure. It would be awesome, too, with how different the end can go. I'd like that a lot.
If they want to make another game with V they're just going to have to pick an ending as canon, due to how some of them pan out.
I can't imagine them using V again. Geralt was a character in his own right that had character traits that were handed over to you to play with. The world was built for Geralt to be in. V was built as a blank slate character to insert yourself into. There's no reason to keep them. I'm pretty sure they only gave the character a name so everyone else in the game could have voice lines for everything and refer to the character by name. It was an attempt to make it a smoother experience, but really, V was a faceless avatar for the player no different to the Fallout games. But because they did the thing with the name it's seamless and everyone sees V as a character, but they're all seeing them as a different character based on how they played. It was pretty clever and I'm sure they'll do it again.
I don't think I agree with you entirely about V being a blank slate. In fact, wasn't this one of the criticisms people had of the game? Many were hoping for a blank slate and an immersive open world where you could be anyone you wanted in Night City, but what was delivered was a linear narrative and a fairly pre-defined character.
Whatever you pick and decide, V will end up being a Merc that was hardened by previous failure and personal loss, and whose personality was shaped by the year with Jackie. You have some wiggle room occasionally, but by and large all the dialogue options and decisions fall under that same umbrella; they're all just different flavours of V, not really options to portray vastly differing characterizations.
I didn't say they should cave to fans save give them what they want. I just think there was a way to say this without being mean about wanting it.
Anyway, I don't have a horse in this race, I still haven't played this. Just commenting on how I think I'd feel if that were me. I've played a fair few games where the ending left me wanting a lot more, and not always because the game was just that good.