I'm not sure how you go from Harald Zwart to Breck Eisner (The Crazies), but I have to assume Sony wasn't too pleased with the returns on The Mortal Instruments: City of Bones and decided to go a different direction, replacing Zwart who directed the first The Karate Kid remake with Eisner for The Karate Kid 2.
I also find it curious it has taken Sony this long to get moving on the sequel to the highly successful 2011 remake, which centered on Dre Parker (Jaden Smith) as he heads to China with his mother (Taraji P. Henson) and eventually learns kung fu from his maintenance man Mr. Han (Jackie Chan). I expect all the principals to return, though that has yet to be confirmed.
The 2010 film was made for a mere $40 million and grossed $359.1 million worldwide and instead of striking while the iron was hot they've wasted four years. Depending on how quickly they get things together, perhaps they can have this ready for Summer 2015 as I'm sure they don't want to wait until 2016 to get it into theaters. [Deadline]