It has already been stated that there's going to be a good chance that the new "Supergirl" TV series would somehow crossover with "Arrow" and "The Flash"...especially due to the fact that they'll all be sharing the same universe. This has almost been confirmed in a recent interview at The Hollywood Reporter with "Arrow" showrunner Marc Guggenheim, indicating that is the direction they are looking to take the new show. He says, point blank, "It's possible."
The article goes on to state that when writer and producer Greg Berlanti made his deal with DC Entertainment to do "Supergirl" at CBS, it was in his contract that the character could appear on "Arrow" and "The Flash." So, there was definitely some thought on his part as to where he envisioned Supergirl fitting in with the rest of the DC TV universe.
Doing "crossover" events of this nature would certainly benefit both networks, and drive up the ratings for each show. It's a win-win scenario, especially since CBS and Time Warner each own 50% of The CW. That fact alone makes all of this very possible and probable.
The series itself will focus on Kara Zor-El, Superman's cousin, "who was born on the planet Krypton and escaped amid its destruction years ago. Since arriving on Earth, she has been hiding the powers she shares with her famous cousin. But now at age 24, she decides to embrace her superhuman abilities and be the hero she was always meant to be."
