Nothing formally announced in the newsypapers other than the Shazam! sequel is part and parcel to the Black Adam movie starring Dwayne Johnston which has been confirmed to be in pre-production.
One educated guess is once The Suicide Squad has completed filming, Producer Peter Safran will have some time on his schedule to get things rolling with Shazam! 2. Zachary Levi, as a 20+ year Hollywood veteran star actor, is the first to put up his hands and defer "It's above my pay grade to comment" when questioned by any interviewer regarding future film studio decisions but one tidbit to consider is Zac did elude to sometime next Summer 2020 when the sequel production could potentially kick-in. Which calendar wise makes sense if New Line Cinema wants their original adolescent cast members under contract to reprise their on-screen characters as they're naturally maturing quickly.