Well the star guardians are likely to get a new set of skins in 2017 or 2018 and as seen with project,it wouldn't be impossible for them to get a new legendary skin along with that.
And I think Syndra is actually one of the better candidates for a second star guardian-legendary skin.
I mean Jinx likely got the legendary skin because her personality wasn't really fitting the star guardian theme as jinx was just too murderous,so the new voice over was a way for riot to make her crazy and battlehungry but in a way that she'd still fit the star guardians.
And I think that Syndra is pretty much in the same boat,as her VO wouldn't fit that well with the star guardian theme,so she would benefit a bit more from a new VO.