Good news, after many announcements yesterday at TechEd 2013 Europe, Microsoft announces Windows 8.1 Preview today during Build conference in San Francisco, CA.
You can go to preview.windows.com and download the update for your Windows 8 x86/x64 and RT devices.
You will be prompted to grab a standalone Windows Update install to prepare your system. When that update is installed - and your device reboots - you will get an immediate prompt to head into the Windows Store and download the entire update.
If you are a TechNet or MSDN subscriber you can download the Windows 8 x86/x64 ISO’s immediately. For Windows RT you must go to preview.windows.com to get it done.
Let's download the bits and start installing evaluations! Hope to upgrade my notebook and Surface RT soon :-)