The Flash season 3 will premiere Tuesday October 4th at 8pm on The CW; Arrow season 5 will premiere in the same time slot on Wednesday October 5th; Supergirl season 2 on Monday October 10th; and Legends of Tomorrow season 2 on Thursday October 13th.
Wentworth Miller was the first to ink a deal that made him a series regular across the Arrow-verse; that means his Leonard Snart/Captain Cold character now has the freedom to appear on Legends of Tomorrow, Arrow, The Flash, and even Supergirl if the stories called for it.
The Legends of Tomorrow trailer had a big surprise as the team come face to face with former Arrow baddie, Damien Darhk.
Cassidy is also expected to make an appearance (in a flashback) in the season five premiere of Arrow.