According to the way it has always been surrounding the Arrow tv show, a lot of people close to Oliver tend to die.
In this case I believe the next person is Roy Harper, and here's why..
You see the guy on the left...yeah well that's the real Arsenal a soon maniacal asshole with a bionic right arm. Basically DC comics version of this guy...
I know there is a somewhat resemblance, but the real truth starts. And bear with me this next part can be very confusing.
The real Arsenal first starts off as the original first sidekick of green arrow know as Speedy who then leaves Oliver's side due to him hating to being referred to as a sidekick.
Soon after he left Oliver's side he donned the new disguise of Red [Arrow](series:720988) who then is captured by Lex Luthor's body guards and the cloned by cadmus tech. Soon after he finds out he was cloned, Roy engaged in a fight with a villain named Prometheus who in then cuts off Roy's arm.
Then Roy changes his name to Arsenal.