HTC has teased their upcoming HTC Desire 820 with an "octa-core 64-bit" SoC. This is referring to Qualcomm's mid-range Snapdragon 615.
Snapdragon 615 uses 8x Cortex A53 (ARMv8) cores and an Adreno 405 GPU. The Cortex A53 cores are designed to replace ARM's Cortex A7 cores.
The HTC Desire 820 will be made official on Sept. 4th at HTC's IFA 2014 event.