I mean, ~20% of the people in the parks are dressed in robes any given day. The wand shops and other HP merchandise stores print money. They are by far the most crowded areas of both their parks on any given day. Why wouldn't they incorporate it into the new park? Using Fantastic Beasts might be a bit of a gamble, but it's kind of moot when many people (myself included) are interested to see how insane the Ministry looks.
Let's be honest, without Harry Potter Universal would not be directly competing with Disney as they are about to be with the new park.