Are there any more Potter books to come?

Nope. All seven have been published.

They are:

Harry Potter and the Philosopher's Stone
Harry Potter and the Chamber of Secrets
Harry Potter and the Prisoner of Azkaban
Harry Potter and the Goblet of Fire
Harry Potter and the Order of the Phoenix
Harry Potter and the Half-Blood Prince
Harry Potter and the Deathly Hallows

Author JK Rowling has mentioned writing a Potter encyclopaedia in future though, so the Deathly Hallows may not be the last ever book about Potter to hit the shops.

In the meantime you could keep yourself amused by re-reading the seven novels, or with the short books JK Rowling wrote for Comic Relief - Fantastic Beasts And Where to Find Them and Quidditch Through the Ages.