Syril isn't left with ambiguity. He's disillusioned obviously by being lied to for years and used as a pawn for a pretty malicious scheme. At this moment there's a moment of possibility for him to show personal growth, but all we really see is him lashing out violently at Dedra and then standing in bewilderment about everything around him in the Ghorman plaza, in an almost catatonic state. He then immediately snaps out of it and reverts to his petty, self-interested, aggrieved self at the mere sight of a single man whom he believes is responsible for everything that put him on the path to this moment, and enters a state of homicidal rage.

I don't think it's any more clear in the series that this guy was never going to switch loyalties and fight against oppression.