The ARM Juno board ships with six 64-bit ARMv8 cores and is intended to show off the potential of ARM's new IP and for helping low-level developers and potential SoC vendors to try out actual ARMv8 hardware. The Juno SoC built by ARM itself has a dual-core Cortex-A57 with quad-core A53 big.LITTLE combination plus Mali-T624 graphics. There's also dual DDR3 memory controllers with this SoC and a Cortex-M3 system controller.
Linaro has already ported the Google Android Open-Source Project to 64-bit ARM along with other software work for supporting ARMv8, which was announced on Wednesday. I'd expect other non-Android Linux OS ports to appear for the Juno board in due time.
While the Juno board is primarily aimed for potential ARM IP licensees and developers porting to 64-bit Android, don't be surprised if you see Linux benchmarks on the ARM Juno later in the summer.