While I’m sure some Survivors would look down upon Eugene jumping right back into the fold so quickly, a moment of heroics at a crucial point in the battle could be enough to get him back in good with his former friends.
More than likely, I think, if he can survive the oncoming war, we’ll see Eugene shift gears back to the Survivors if things go their way.
While he has been treated well by Negan, I don’t imagine that allegiance lasting should things start going bad, and Eugene is smart enough to know life in Alexandria is not ideal despite his current status.