EW is reporting that the next CW Arrowverse crossover “Crisis on Infinite Earths” will be the network's largest yet, crossing over Arrow, The Flash, Supergirl, DC’s Legends of Tomorrow, and Batwoman, airing over five hours and over two quarters, as announced by the CW at its upfront prresentation to advertisers in New York Thursday.
The first two episodes will air in December, with the concluding two episodes airing in January.
This past season's "Elseworlds" crossover only involved Arrow, The Flash, and Supergirl. Black Lightning apparently remains separate (for now) from the annual crossover.
Both Arrow and The Flash's recent season finales teased the event.
The Flash, Supergirl, Arrow, and Batwoman will air this fall and DC’s Legends of Tomorrow will return as a mid-season replacement.