It seems like SM Entertainment's soon-to-debut girl group aespa has four members in total.

On October 28, SM Entertainment's founder/head producer Lee Soo-man attended the '2020 World Cultural Industry Forum'.
During the event, Lee Soo-man gave a glimpse of his agency's rookie girl group aespa, which was announced to debut next month.

▶ [SBS Star] SM Ent. Is Launching a New Girl Group for the First Time in 6 Years
In the video, a total of four members were seen and introduced as the members of aespa.

Although it is still not confirmed whether the group will consist the four girls shown in the video, fans are assuming that the group will debut as a four-member group.
Currently, SM Entertainment dropped teaser photos for only the two members of aespa―WINTER and KARINA.
Check out the video below to better understand aespa's 'Avatar X Experience' concept.
 
(Credit= 'aespa' YouTube, SM Entertainment) 

(SBS Star)