Colton Haynes Probably Isn’t Coming Back to Arrow Anytime Soon
Colton Haynes luckily escaped Arrow before the downhill trend of the show really started to sink in near the time of his departure at the end of season 3. He did make a guest appearance one episode in season 4, and there's even been talk of him returning for a bigger role in the oncoming seasons. However, it seems that talk was likely all it was, as Wendy Mericle, producer of Arrow, gave some insight to TV Line about the show's current plans for Arsenal's return:
While that doesn't rule out a return sometime in the future, it would seem that Mericle's comments would suggest that fans probably shouldn't be expecting Haynes to return to the show anytime in season 5.
Colton Haynes' Arsenal is a reminder of Arrow's finer moments, and it would be great to see him back on the show. However, Arrow is definitely a different beast now than it was during its prime. Oliver's character development has gone out the window, and relationship drama has taken center stage over plot, action, choreography, and just about everything else, which is incredibly sad to see considering how compelling Arrow used to be.
Hopefully, Arrow can course correct, but from the first trailer from season 5, things are looking very similar in style to what was done last season. It would be great if the show pulled it together, but it's questionable how likely that is to actually happen. Arrow Season 5 premieres on October 5th, 2016.