No, The CW isn’t folding FOX’s Gotham into the Arrowverse, but they will be bringing their own version of the city, as well as one of its heroes to their next big crossover event. EW is reporting that Arrow’s Stephen Amell made the announcements at today’s upfronts for the network:

“We’re incredibly excited to announce that we’ll be doing another crossover event this fall on the CW, and we’ll be introducing a new character. For the very first time appearing, we’ll be fighting alongside Batwoman, which is terrific. The crossover is going to make it to air in December. I need to leave right now and start filming it.”

Unfortunately, the announcement didn’t include a reveal of who would be playing Batwoman, or how the TV take on her character will compare to its current comic book version.

Source: EW