Peter Jackson formally announced this afternoon that his take on “The Hobbit” — originally envisioned as a two-part adaptation of J.R.R. Tolkien’s tale — will be a trilogy. The Oscar-winning filmmaker — who, as Smeagol scholars are well aware, directed the “Lord of the Rings” trilogy to much critical acclaim and financial success — had hinted about a third “Hobbit” during a recent appearance at Comic-Con.