Good news from one of the largest software company. Microsoft will release Windows 10 on July 2015. The better news is, Windows 7 and 8.1 users can upgrade freely to the latest OS. It's also avaialble for free if you buy a new PC with the OS pre-installed. If you buy a Windows 8.1 device before end of next month, also will get the Windows 10 for free as an upgrade.
Windows 10 is compatible with Microsoft's PCs, tablets, phones, Internet of Things, Surface Hub, Xbox One, and HoloLens. The initial OS release will be limited to phones and tablets. A Windows 10 upgrade for Windows Phone 8.1 devices will vary by phone makers and carriers.
Starting today, those on Windows 7 and Windows 8.1 will be able to reserve an upgrade via a prompt that should appear in the PC's taskbar. Click "Reserve your free upgrade" when it appears, add an email for confirmation, and you're all set. When it's ready, the upgrade will require 3GB of space.
Hopefully the OS is as good as Windows 7.