So! It's been nearly a year now, about a month away, and I get to state my thoughts with the benefit of that time having passed.
It actually feels like it's been a couple years since this thing released, but I think that's just because Soul Calibur IV was the last actual Soul Calibur game when it comes to story and available characters, so it was the last game I will ever play in the series unless the crap done in SCV is properly made up for.
If we could go with any approach no matter how unrealistic, I would suggest doing what I have previously suggested for FF13: release a brand new game with all the appropriate elements (most important among them being that all the characters that were pointlessly kicked out of the series return, especially Sophitia and Taki), call THAT game Soul Calibur V, and re-label what we are currently calling Soul Calibur V as something completely different. Maybe something to reflect that it's an alternate universe so we don't have to deal with the crap Daishi pulled to get rid of iconic characters to realize his own fanboy wet dreams. Newly introduced characters like Viola could still come back in the main franchise from a new starting point.
I acknowledge how absurd many people feel the concept of "re-release new game as title of existing one and re-label existing one to something else" would be. But it worked out splendidly for two franchises. People in the West were introduced to Final Fantasy IV and Final Fantasy VI as being Final Fantasy II and Final Fantasy III, yet today people know all the games by their proper names. And the Mortal Kombat reboot was simply named Mortal Kombat, and nobody really had a problem with that.
Barring that, if that's not possible, then I say make a "sequel" but with two caveats. One, again, all the characters that were needlessly removed, especially Sophitia and Taki, return, and the entire focus of the game is on them, NOT on Daishi's fanfic characters. And two, just for that one sequel, no Ivy. Would a removal of Ivy happen? No, not realistically. But I think that since Daishi had to be toolish enough to remove Sophitia and Taki for stupid reasons when they were iconic to the series and had a place in every entry (Sophitia returned for the console version of SCII), then it's only fair for Ivy to be forced to sit out one entry in the franchise while Sophitia and Taki are in the game.
I am not on board with the ideas of a reboot or a prequel. Neither case would rectify the damage Daishi has done to the story and character aspects of this series. Both ideas amount to cop-outs, a way of sidestepping the actual problems introduced by Soul Calibur V rather than confronting and dealing with them. Based on Daishi's behavior and comments in interviews, it is very likely that if he did make a prequel, it would be a hollow gesture toward old fans. "Here's your beloved characters again, give my vision for the series another chance!" This would be followed by a post-SCV sequel where he ruins the story further and old characters like Sophitia and Taki still aren't playable. Meanwhile, a reboot in this case would say "Okay, here's a new universe where you get all your favorite characters back, but it's not the REAL Soul Calibur universe, that one's where Soul Calibur V happened, Sophitia died and Taki is somehow too old to be a ninja but Mitsurugi is magically not too old to be a samurai."
If neither of the above could happen, then I'd rather never see another Soul Calibur game released. If Daishi can't treat the story and characters with the respect they deserve, then let them die with what little dignity they have left. Send the gameplay aspect, which is the only part he seems to give a damn about, off to a brand new IP.