Windows 10 to be available on July 29, free upgrade

Hello World: Windows 10 Available on July 29
It will be a free upgrade for all Windows users...
Will it get 1 billion users as expected?
Announced by Cortana, sounds very good.
Upgrade to Windows 10 - July 29th by Windows Blogs @ SoundCloud

How to reserve your free copy of Windows 10 - CNET