The area pictured above is inside Universal Studios and will be called "Wizarding World of Harry Potter - Diagon Alley". It will be modeled after London and will have a major ride where visitors ride cars through a labyrinth of passageways populated with dragons and other characters based on Gringott's Wizarding bank from the J.K. Rowling novels.
There will also be shops and eateries like on the Islands of Adventure side and other novelties not yet revealed. Diagon Alley, located on the site of the old Jaws Ride, will be connected to the Wizarding World of Harry Potter at Islands of Adventure by the "Hogwarts Express" train ride.
There has been so much interest and speculation about the expansion, The folks at Universal and Warner Bros. decided to release the proposed expansion to the public to boost interest in the parks. The entire project is set to open sometime in 2014. Exact date to be announced sometime in the future.
Since the Harry Potter project will span both parks, it's likely visitors will need a 2-Park Pass to see the whole thing but it will be well worth it. Tickets and packages can be purchased on Universal Studios Orlando website. Shop around and see what kind of deals you can secure from other travel sites as well.
Although an opening date hasn't been firmed up yet, the parks usually open newer attractions prior to the summer months to maximize visitor enjoyment so I'm going to venture a guess it will be ready in April or may 2014. We'll see.