Arrow's final season (I'm not crying...YOU ARE) arrives on October 15th at 9pm after The Flash. This sets up the epic crossover Crisis on Infinite Earths.
Supergirl moves to 9pm on Sundays to make room for Batwoman. She flies to save Earth-38 on October 6th.
The Flash arrives on the CW Tuesday, October 8th. Oh, and it looks like Cisco is back for the next season.