On Microsoft's earnings call for its fiscal Q1 2019 earnings, Microsoft CEO Satya Nadella revealed that Windows 10 is now the most dominant operating system in the enterprise market. But this means that a significant percentage of machines are still running Windows 7, an operating system which will cease to receive security updates just 14 months from now.
ARS Technica warns this looks a lot like what happened with Windows XP:
This leaves just 14 months for most businesses to migrate away from Windows 7. The last "big" migration in the corporate world was from Windows XP to Windows 7 in the run-up to Windows XP's end of life in April 2014. At a comparable stage in that transition, Windows 7 had 45 percent of the installed base, to 38 percent for Windows XP. Those proportions aren't too far off current estimates for the Windows 10/Windows 7 mix: StatCounter puts things at about 48 percent for Windows 10 to 39 percent for Windows 7.