We also don’t know the exact reason behind those delays on Sony’s side, and there have been various theories put forward by fans, including problems related to the Snapdragon 810. Still, Sony haven’t discussed the problem in detail, and have been keeping mostly quiet about the delays surrounding the Z4’s release, so we have no official information.
On the other hand, some experts have been commenting that Sony definitely need to make this release a successful one, as the company has been having some issues on the market lately, with various of their devices performing somewhat poorly.
With that in mind, the Xperia Z4 Tablet could be their last true shot at regaining their lost market positions. If it’s a successful release though, it should definitely get that job done and more. Until then, Sony first have to resolve their development issues that are preventing them from releasing the device – and hopefully those issues aren’t going to leave a lasting mark on the final product.