Okay, so we all know that after Sprout leaves, Neville becomes the new Herbology professor. And (of course) that means that Neville becomes the new Head of Gryffindor House because, why not?
And we can all assume that Flitwick is still alive and kicking and flaunting his adorable little self through the Hogwarts as the Head of Ravenclaw. And Slughorn is probably still around as the Potions professor and Head of Slytherin.
But, after Sprout leaves, McGonagall is left without a Head of Hufflepuff. And none of the current professors are Hufflepuff alumni. Until...
On September 1st, after the new first-years have been sorted, a blonde-haired witch bursts through the doors to the Great Hall and struts her way over to the staff table. All of the students are staring and wondering who fhis woman is until McGonagall, smiling at her, stands and says: “Welcome back, Miss Abbott.”
Hannah Abbott-Longbottom looks over at her husband (who is flabbergasted as to why his wife is there) and winks before turning to the students.
“Hello, witches and wizards of Hogwarts. I am Professor Abbott-Longbottom, and I am your new Muggle Studies professor and Head of Hufflepuff house. All I can say, is... I’m glad to be back.” She walked around the table and took her seat next to Professor Flitwick.
Neville turned to the Headmaster. “How did you convince her?”
“Well, Mr. Longbottom, it didn’t really take much. All I had to do was promise her that Hufflpuff will finally win the House Cup for once.”
And that’s the story of how Hogwarts reinstated the Muggle Studies class for the first time after the Battle of Hogwarts.