The DC-CW superhero shows will be doing a special "Crisis on Infinite Earths" events in the fall of 2019. The news was announced in the closing moments of Wednesday's Supergirl - itself the finale of this week's "Elseworlds" crossover event.
The "Elseworlds" crossover event seemingly seeded several things for this fall 2019 event, including the debut of Psycho Pirate (played by Bob Frazer), and Arrow (Stephen Amell) making an unspecified deal with the Monitor.
Amell tweeted out the logo for the 2019 event, with an emoji:
Details on what shows would be involved were not announced; the CW has not announced which shows will return in fall 2019 - or even debuting, such as the teased Batwoman series.