Arrow season 3 premieres on October 8th at 8 pm on the CW with it's 3 season. My predictions for season 3 is that Oliver tells Diggle that he can't be apart of the team because of his new baby and Diggle get's very upset by this. Somewhere else wee going to see Malcolm training, then appears Thea training with him. I believe that Thea becomes his apprentice and that mid-season she's gonna fight Oliver and Roy but both teams help each other.
In the beginning of season 3 where gonna see Oliver training Roy to be his Partner and help him patrol Starling city and to become a hero himself. The addition of Wildcat into the series will show Laurel and him training in boxing and helping her become maybe the Black Canary if the shows gonna go that way in the comic universe.
Finally, my last prediction is about Ra's Al Ghul. I believe he comes to kill Merlyn but Oliver knows Thea's there so Oliver interferes and try's to stop them then Merlyn and Oliver team up on and off through out the season to try and stop Ra's Al Ghul.
that's my predictions! see the season 3 trailer now.