Microsoft has announced Windows 10 and skipped windows 9 and it is gonna release in 2015. According the Microsoft a large number of devices are going to run this because of its compatibility with all of them.
In January I posted about the announcement of windows 9, but now they've skiped it in favour for Windows 10.
As Microsoft said:
Windows 10 will run across an incredibly broad set of devices – from the Internet of Things, to servers in enterprise datacenters worldwide. Some of these devices have 4 inch screens – some have 80 inch screens – and some don't have screens at all. Some of these devices you hold in your hand, others are ten feet away. Some of these devices you primarily use touch/pen, others mouse/keyboard, others controller/gesture – and some devices can switch between input types.
In the Windows team, we're proud of this – but we also know that the world today is very different from the one in which Windows grew up. Today, devices outnumber people. Connectivity is like oxygen. The tension between the desire for agility versus stability poses a huge challenge for IT Pros. Experiences – no matter what device you're on – just need to work. The only thing that hasn't really changed is the situation for developers – still too much to do, and not enough time.
Windows 10 is providing application platform for developers which will help them to build apps easily for all of the devices having different screen size. There'll be one store to search and download apps from.
Microsoft is combining the experience of windows 7 and windows 8 together in windows 10. Aero transparency is back and start menu looks like that of windows 7's but it also has metro styled tiles. Microsoft will give you option to customize start menu as you like.
Can I download preview right now?
Yup, you can. Join the Windows inside program and download preview .iso file of the windows 10 and check that out.
Note: Don't install it on your main device. You can install windows 10 preview on some virtual machine (Preview is not stable).
Source: Windows blog