I'll join @CCB and also predict 30-35 medals and I'm going to be ambitious and say 12 gold, equalling our Sydney 2000 record of gold medals.
I agree with CCB we don't have that many clear gold medal chances, but my hopeful prediction would be, in no particular order:
Women field hockey team
Track cycling team sprint
Harrie Lavreysen (individual sprint)
Harrie Lavreysen (keirin)
Niek Kimmann (BMX)
Mathieu van der Poel (Road cycling race)
Sifan Hassan (road marathon)
Rowing W1x
Rowing M2x
Rowing M4x
Bart Lambriex/Floris van de Werken (skiff)
Luuc Van Opzeeland (IQfoil)
It's crazy that some of our most elite athletes Marrit Steenbergen, Femke Bol or Demi Vollering/Lorena Wiebes are not in this list, but their competitors O'Callaghan, McLaughlin and Kopecky are even stronger.
Edit: forgot Puck Pieterse somehow! I guess Ferrand-Prevot wins this one...