According to the KSite the DC television by The CW, such as Arrow, The Flash and DC’s Legends of Tomorrow previous seasons will be released on the same day as their new season premieres on Netflix.
Making Gotham not the only DC television series that will have its previous season released on Netflix on the day that the new season begins on network televsion.
The Flash season 2 will be available to stream on October 4th, coinciding with the season 3 premiere.
Arrow season 4 will be available to stream on October 5th, coinciding with the season 5 premiere.
DC’s Legends of Tomorrow season 1 will be available to stream on October 13th to coincide with the season 2 premiere.