Druids, Rangers, Wizards, Warlocks, Paladins, all have class features relating to the Beasts .
Plus. Pets. Cute pets. Winged kittens. Wolf puppies. T-Rexes.
It is almost already making money now just thinking about it.
As mentioned, the Players Handbook will have a sampling of Beasts necessary for play. But the Bestiary (Beastyary) will elaborate on the very many different kinds of Beasts.
Animal amalgams, like Owlbear, Griffon, Hippogriffin, Pegasus, Drakes, etcetera, can type as Beasts.
Anything relating to Beasts − Wildshape, Familiar, Companion, Mount, Feat − can expand via the Bestiary.