Where are you even getting all this stuff about Virgil even being an important character at all much less him being our archrival "Arcas"? Is this something you're making up or you're leaking it? Not very sporting to make bets if you have insider info.
Some source material, Vampire the Masquerade.
Some dev talks.
Some speculation based on events.
A lot of it is pretty obvious. We know something big is happening and shits about to go down with goddesses. We know Calisto is Inanna's prime player and she has enemies. Based on how things have gone with the girls most of us know Carmen is going to get turned (like I said earlier, i'm 100% sure that's happening).
We know the devs have no problem killing off main characters and hints have been dropped that not every love interest is going to make it to the end. Laurie could die this update, I think something similar will happen to Carmen and why she needs turning but I think some will be unavoidable.
Virgils role is guesswork but based on his character and information we have on him it's a pretty solid guess.
Devs have dropped some subtle and not so subtle hints so it's a lot of building a jigsaw and seeing what peices fit where in the story and then trying to fill in the blanks as best as possible.