Yeah they kinda dropped that after it was mentioned by Deadshot. Might be mentioned next episode but Diggle has taken a backseat most of this season. I think it's a given she will die. I think episode 19 or 20 the episode title is something to do with red (maybe seeing red). I think that's when it happens. Or the finale. I hope Slade is a re-occurring villain throughout the shows run. Don't want him to 'die' at the end of this season. Merlyn, like Diggle, has almost been forgotten. As has Isobel Rochev, the mysterious person who employed Fyers in season 1 on the island. Lots of potential stories to go on. I doubt they're all dealt with this season.