The 9to5Mac resource found in the code of the previously merged build of iOS 14 a mention of the Catalyst version of the iMessage application.
This means that Apple will transfer most of the features of the program from iOS to macOS, including stickers and effects. Now on poppies you can only receive and send messages.
Although Apple previously released Catalyst-based applications Dictaphone, Promotions, and Podcasts, they never appeared on computers. So it is not known what to expect from the new development.
In any case, we will see all the changes in a month at WWDC 2020. [ 9to5 ]