Constantine Rumored For DC's Legends Of Tomorrow; Flash For Supergirl
According to Bleeding Cool, a "Thanksgiving Day source" has filled them in that Grant Gustin will appear as The Flash next May in Supergirl.
Regarding Constantine, it's said that the cast of DC's Legends of Tomorrow will be switched up each Season, with Matt Ryan set to return as Constantine as a series regular for Season 2 of DC's Legends Of Tomorrow in 2017.
Another tidbit notes Steven R McQueen will be cast as a new hero for Season 2 of DC's Legends Of Tomorrow. McQueen was previously vying to play Nightwing.