The CW has really capitalized on the popularity of their DC shows with week-long crossover events that combine the characters of Supergirl, The Flash, Arrow, and Legends of Tomorrow. Of course, the problem is that Supergirl takes place on another Earth than the other three shows, so she doesn't get to play with the other kids very often.
But according to Entertainment Weekly, that is about to change this season. Executive producer Andrew Kreisberg says, "Kara and Alex are at the center of it through all four hours. One of the things we’ve been doing a lot this season is getting back to Season 1 and really making it Danvers sisters-centric, so a lot of what’s going on this season is Kara and Alex doing things in tandem, and the crossover won’t be any different.”
One still has to assume that The Flash will have to go to Supergirl's Earth and bring her and Alex back to his Earth, because that seems way easier than trying to transport a dozen or so characters (how many Legends are there now?) to Supergirl's Earth.
How do you see it playing out? Let us know in the comments!