The DC Extended TV Universe is set for even more elaborate crossovers. “Arrow” & “The Flash” are doing great over at The CW, but “Supergirl” at CBS is starting to wain after some initial buzz.

According to Bleeding cool The network are now proposing to crossover  the entire cast of “The Flash” into Supergirl, for a special crossover episode that will air next May during sweeps week.

Talk of further expanding the DC TV Universe to encompass Supergirl has been around for some time, but CBS were initially reluctant. Supergirl, Arrow, The Flash and DC’s Legends of Tomorrow are all made by the same production company and have many of the same producers, so a crossover is in the realms of possibility,  if both networks are willing to play ball.

With “Supergirl’s” strong premiere ratings now on the decline, the move would make sense, to help get some interest back into the CBS show. The crossover would depend on the network wishing to extend the first season from its currently scheduled 13 episodes, with an option of a back nine, for a full 22 episode run.

The same site goes onto suggest that Matt Ryan’s John Constantine will be popping up in the DC Extended TV Universe again, this time as a season regular in season 2 of the superhero team-up show,  “DC’s Legends of Tomorrow”. This would collaborate stories of the show switching up its roster of heroes from season to season.