Apple may have the first 64-Bit mobile processors with the A7 chip it uses in the iPhone 5s and iPad Air but now Qualcomm is looking to follow suit with a duo of mobile processors featuring 64-Bit instruction set slated for late 2014, while most Android apps are just starting to be written for multiple-processors, the jump to 64-Bit processors is acknowledged as a future-proofing move as well as the natural progression of mobile's evolution. It might take as long as a year for us to see Android or Windows Phone apps that can take full advantage of 64-bit architecture.
Source: Engadget