Today, Google added the 64-bit Intel images (Windows, Mac OS X and Linux) to its Android emulator, signaling the fact that developers can now start testing their Android apps for 64-bit Intel-based devices. The support for x64 chips will increase the amount of addressable memory (devices will be able to use more than 3 GB of RAM), and developers will get access to more registers.
If this doesn't sound particularly interesting, it's because it's not the "64-bit platform" most were expecting. With merely a week before Google is supposed to launch Nexus 6 and Nexus 9 running Android L, it's a little strange that the company hasn't added support for the 64-bit ARMv8 platform.
ARMv8 is supposed to bring much more than support for 4 GB (or higher) RAM, as well as a bigger register count. It's ARM's next-generation architecture with a cleaner and more efficient design, native support for hardware encryption (which is much needed for Android L's out-of-the-box encryption, unless you want to spend more than an hour encrypting your local data), and improved general performance, too.
Chips on ARMv8 tend to have 10-20 percent extra performance automatically, compared to the same chip on ARMv7, so the new ARMv8 chips should get higher performance not just from new CPU micro-architectures like Cortex A57, but from the underlying architecture itself, too.
There are a couple of possible explanations for why Google didn't add support for ARMv8 at this time. One would be that these x64 images were actually developed by Intel, and Google just added them to the emulator without waiting for its ARMv8 support to be ready.
The second theory would be that Nexus 9 won't be based on Nvidia's Denver CPU, which means none of the Android L devices launching soon will need ARMv8 support. However, it's unlikely that Google would release Android L without ARMv8 support built in, considering devices like the HTC M9, Galaxy S6 and Xperia Z4 should all use an ARMv8 chip early next year, before Google gets a chance to release another major Android version. Releasing "L" without ARMv8 support wouldn't make too much sense.
Android L should already support ARMv8 by default, thanks to its Linux kernel version 3.10 (ARMv8 support was added in version 3.7), but it's possible that Google needs some additional kernel features and ARMv8 support for the Android operating system itself.
If Google does indeed ship Android L with full ARMv8 support as it promised earlier at Google I/O 2014, then it should add ARMv8 support for the emulator soon, too, because developers will need to start testing their apps for the new ISA.