I agree. I saw him on San Andreas and it was a very small part for him. He had a job in Arrow, and let's be honest, not everyone has that oportunity to play an imporant comic book hero like Arsenal is, so why would he leave? I'm not seeing any projects so I'm intrigued. I live with the idea that he'll come back but I may be wrong and probably, he will only be on Arrow as a guest...
Also I think that I won't accept another romantic interest for Thea