Microsoft plans to skip Windows 9 and jump straight to Windows 10 with a major update that is coming to laptops and tablets as well as Windows Phones. The look of Windows 10 will change depending on the device you are using, which should deliver a better user experience.
You don't need to buy a new PC to get Windows 10. If your computer can run Windows 8, it can run Windows 10. Older computers can upgrade, but it will be a pain to upgrade from Windows Vista to Windows 10. Windows 10 is a free upgrade for Windows 7 and Windows 8 users for the first year.