The Flash: 10 Major Predictions For Season 3
6. Captain Cold, Malcolm Merlyn, And Black Canary
Wentworth Miller's Captain Cold has long been established as a regular player on The Flash, even if he did depart last year to join Legends of Tomorrow. So seeing him back isn't too big a stretch. Joining him, however, will be at least two characters very much rooted in Arrow: Malcolm Merlyn and Laurel Lance.
John Barrowman and Katie Cassidy have, alongside Miller, signed special contracts to appear as Arrowverse regulars, meaning we could feasibly see them appear on any of the four shows. So it seems a safe bet that we'll be seeing them on The Flash, and a good chance it could involve the crossover too. Cold and Merlyn are both a part of the Legion of Doom on Legends of Tomorrow, alongside Reverse-Flash and Damien Darhk, and having these renowned and fan-favourite villains of Arrow and The Flash appear during the crossovers would make a fair bit of sense.
As for Laurel, the Black Siren who appeared on The Flash was the best the character had been in a long time; the show offering the chance to put the character to better use is one they may want to take again.