It seems quite clear that Harley’s attention will be elsewhere for the duration of the film, so it’s unlikely that Jared Leto’s Suicide Squad Joker is going to get much more of a mention than that in the new movie.
The voice over says that Harley and Joker broke up.
The trailer does catch us up on what’s going on with Harley and her “puddin'” but with knives being thrown at a dart board drawing of Joker by Harley, it’s clear that the pair are on the outs.